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Yorkville 100watt Mixer/Amp - Replaced Transistors
- Thread starter Jason G
- Start date
Sir Jason . . . . . . .Geeeeee
O.K. then . . . . that maintaining of the differential pair of voltages . . .equally . . .as well as their same degrees of loadings, allays that suspicion of a "lazy" filter capacitor of a conjunct power supply pair.
I now leave this for you to muse over, before I can deploy its info towards the next situation.
Since the audio of music that we hear is a complex and variable and changing mix . . . .as well . . .with its speech / vocals.
The outputted audio is copycatting the same info, but at higher voltage and power levels.
For the next test we are needing a tone to feed into the amp and amplify while we do some differential voltage testing.
In my case, I just pull out one of several options of audio signal or function generators.
OR . . . . . old school style, I could pull out a vinyl record from the 60-70's that had test audio on one side and the whole opposite side had looooooong periods of test tones for a whole 30 minutes.
Or . . . . . go the cassette player / recorder route and record the accompanying test tone from a TV station after it goes off the air and leaves on a test pattern for a period of time.
Or . . . . . if finding myself afar, upon the steppes of the Himalayas . . . . . or at a distant Timbuktu.
I could scavenge for a mere small signal NPN transistor, 4-5 resistors and three like value capacitors ,an output coupling capacitor, a 9V battery and then cobble up myself a phase shift audio test oscillator.
OR . . . . current times . . . . . you could get any tone needed from your computer's audio port and internet linkage to audio source options.
Ditto . . . . on using a much smaller Smart phone with proper interconnective wiring.
Same . . . . for an I-pad or an Amazon Fire tablet . . . or like variants of other companies . . . . and using their audio output headphone jacks.
Noooooooooooo . . . now you COULDN'T actually be HAVING have an audio generator . . . nor borrowing access to one ?
NOR . . . . could you have ONE of the very-very few systems that have a push button and BAAAAAAMMMMMMM
there is being a 400 / 1000 ~ audio tone for testing of R-L stereo speaker balancing, or phasing of interconnected speakers.
Think over your possibilities . . . . and I will then fill you in on the magic to follow.
Although, this certainly suggests of a power supplies limitations on its progressive power demands.
Also, think about if you have an AC power line isolated audio amp for stage by stage audio signal tracing . . . .
The main unit of a computer speakers pair, coming to mind, along with an audio patch cord with its RCA plug ends .
73's de Edd
.....
O.K. then . . . . that maintaining of the differential pair of voltages . . .equally . . .as well as their same degrees of loadings, allays that suspicion of a "lazy" filter capacitor of a conjunct power supply pair.
I now leave this for you to muse over, before I can deploy its info towards the next situation.
Since the audio of music that we hear is a complex and variable and changing mix . . . .as well . . .with its speech / vocals.
The outputted audio is copycatting the same info, but at higher voltage and power levels.
For the next test we are needing a tone to feed into the amp and amplify while we do some differential voltage testing.
In my case, I just pull out one of several options of audio signal or function generators.
OR . . . . . old school style, I could pull out a vinyl record from the 60-70's that had test audio on one side and the whole opposite side had looooooong periods of test tones for a whole 30 minutes.
Or . . . . . go the cassette player / recorder route and record the accompanying test tone from a TV station after it goes off the air and leaves on a test pattern for a period of time.
Or . . . . . if finding myself afar, upon the steppes of the Himalayas . . . . . or at a distant Timbuktu.
I could scavenge for a mere small signal NPN transistor, 4-5 resistors and three like value capacitors ,an output coupling capacitor, a 9V battery and then cobble up myself a phase shift audio test oscillator.
OR . . . . current times . . . . . you could get any tone needed from your computer's audio port and internet linkage to audio source options.
Ditto . . . . on using a much smaller Smart phone with proper interconnective wiring.
Same . . . . for an I-pad or an Amazon Fire tablet . . . or like variants of other companies . . . . and using their audio output headphone jacks.
Noooooooooooo . . . now you COULDN'T actually be HAVING have an audio generator . . . nor borrowing access to one ?
NOR . . . . could you have ONE of the very-very few systems that have a push button and BAAAAAAMMMMMMM
there is being a 400 / 1000 ~ audio tone for testing of R-L stereo speaker balancing, or phasing of interconnected speakers.
Think over your possibilities . . . . and I will then fill you in on the magic to follow.
Although, this certainly suggests of a power supplies limitations on its progressive power demands.
Also, think about if you have an AC power line isolated audio amp for stage by stage audio signal tracing . . . .
The main unit of a computer speakers pair, coming to mind, along with an audio patch cord with its RCA plug ends .
73's de Edd
.....
Hey! haha love the replies and I really enjoy reading your writing style!
So I can easily use my phone/laptop to generate a test tone at whatever frequency you require and run that through the amp. I could also bring my amp to a engineer friend who has a scope at his office to do really deeper analysis.
For now i'm hoping there is more I can test/troubleshoot on my own with a DMM and a test tone as you mentioned.
What is the best way to move forward, will you write out a test plan and i'll execute and reply with my results?
So I can easily use my phone/laptop to generate a test tone at whatever frequency you require and run that through the amp. I could also bring my amp to a engineer friend who has a scope at his office to do really deeper analysis.
For now i'm hoping there is more I can test/troubleshoot on my own with a DMM and a test tone as you mentioned.
What is the best way to move forward, will you write out a test plan and i'll execute and reply with my results?
Further in-depth testing would best be done with a test tone and oscilloscope.
Tracing the signal through from input to output at the appropriate levels (low to high) will soon reveal the point of distortion.
It is possible to get an oscilloscope function through the input of a soundcard (PC) for which there are software packages (many free) online.
Tracing the signal through from input to output at the appropriate levels (low to high) will soon reveal the point of distortion.
It is possible to get an oscilloscope function through the input of a soundcard (PC) for which there are software packages (many free) online.
Ok, now given my limitation of electronics knowledge could this still be something I can test/measure and report back to you all? I'm at a loss at where to begin (Exact locations on the PCB to test)
Looking back at my first post and the spec on the transistors i installed vs the stock ones, is there any amount of confidence that the spec difference (although to my eyes very minor) can be the culprit and maybe I should focus my energy on finding the exact same transistors?
Are there other components that high a decent probability of being the issue and maybe for the cost i should just replace them anyways?
I thank again all those who have given me their time so far. I really hope i can resurrect this amp back to 100% working order.
Looking back at my first post and the spec on the transistors i installed vs the stock ones, is there any amount of confidence that the spec difference (although to my eyes very minor) can be the culprit and maybe I should focus my energy on finding the exact same transistors?
Are there other components that high a decent probability of being the issue and maybe for the cost i should just replace them anyways?
I thank again all those who have given me their time so far. I really hope i can resurrect this amp back to 100% working order.
Sir Jason . . . . . . .Geeeeee
A continuance . . .
OK on the test tone capability.
Lets go to the RA16 base resistor at the BC560 at the input of the Audio Power Output stage and couple a tone into that with a ground at that bottom side of the resistor and use an isolative 0.1 ufd cap at the top of that resistor to couple the audio in thru.
That way, the paper / poly / or ceramic coupling capacitor gives circuitry DC isolation.
Since we are far past any volume control circuitry, you will have to start with the tone level at a minimum and slowly bring it up to see if you are then able to exceed the level that you had initially experienced your audio distortion, when it (or audio) was passing thru the WHOLE system.
Testee-Testee
73's de Edd
.....
A continuance . . .
OK on the test tone capability.
Lets go to the RA16 base resistor at the BC560 at the input of the Audio Power Output stage and couple a tone into that with a ground at that bottom side of the resistor and use an isolative 0.1 ufd cap at the top of that resistor to couple the audio in thru.
That way, the paper / poly / or ceramic coupling capacitor gives circuitry DC isolation.
Since we are far past any volume control circuitry, you will have to start with the tone level at a minimum and slowly bring it up to see if you are then able to exceed the level that you had initially experienced your audio distortion, when it (or audio) was passing thru the WHOLE system.
Testee-Testee
73's de Edd
.....
Would you be able to guide me on exactly where to connect this input to the audio output stage? I just want to ensure i do it right. Maybe you could mark up the schematic including how i would wire up the .1 ufs cap (if you have a model of cap to buy that would be sweet!)
And back to the question about transistors, never heard if anyone thinks maybe this is all due to the spec of the transistor being slightly off?
And back to the question about transistors, never heard if anyone thinks maybe this is all due to the spec of the transistor being slightly off?
Sir Jason . . . . . . .Geeeeee
Here are the inputs for the tone.
The signal lead could go to the same options of:
The base of BC560 . . . . Q16
Or bottom lead of 100K . . . . . RA16
Or that bare jumper wire that is between the two green pads.
Audio ground could go to the top lead of 100K R16.
BTW what was your initial audio test source being, and into which of the 4 or more possible audio inputs of this unit.
PCB FOIL LAYOUT . . . . . SNIPPET
73's de Edd
.....
Here are the inputs for the tone.
The signal lead could go to the same options of:
The base of BC560 . . . . Q16
Or bottom lead of 100K . . . . . RA16
Or that bare jumper wire that is between the two green pads.
Audio ground could go to the top lead of 100K R16.
BTW what was your initial audio test source being, and into which of the 4 or more possible audio inputs of this unit.
PCB FOIL LAYOUT . . . . . SNIPPET
73's de Edd
.....
OK awesome, i will test this tonight and report back. Do you want me to report simply if there is distortion similar to through the normal pre-amp phase?
As for audio test, i ran my phone and played some music, used all front inputs (except for the XLR)
I also plugged in my electric bass guitar and same thing, nice clean good sounding tone until i hit a certain volume, then i hear distortion. I may record a quick youtube video with a mic on the speaker cab so you can get a sense of what is going on.
As for audio test, i ran my phone and played some music, used all front inputs (except for the XLR)
I also plugged in my electric bass guitar and same thing, nice clean good sounding tone until i hit a certain volume, then i hear distortion. I may record a quick youtube video with a mic on the speaker cab so you can get a sense of what is going on.
Sir Jason . . . . . . .Gee
HEY ! I see that the balls been lobbed back into my court . . . how you do dat ? . . .you sneaky . . .velly- velly sneaky !
The best logic would be the initial evaluation of the final . . .power output stage . . to see how it responds, and if being flawless . . . to move to the sequential intervening prior signal handling stages.
73's de Edd
.....
HEY ! I see that the balls been lobbed back into my court . . . how you do dat ? . . .you sneaky . . .velly- velly sneaky !
The best logic would be the initial evaluation of the final . . .power output stage . . to see how it responds, and if being flawless . . . to move to the sequential intervening prior signal handling stages.
73's de Edd
.....
Ok, finally got around to your test. Audio signal on RA16 and the bare jumper wire beside it. Same exact outcome. Regardless of music or a straight frequency signal the behaviour is similar. Clean signal up until a certain point and then the distortion happens. I will try to record a video to show you.
I believe its safe to say its nothing for sure in the pre-amp stage.
I was thinking to start just replacing some components. This was my list so far.
Would love to know your thoughts and what else i can do/try or should I just start replacing components?
For the cost and if the risk is minimal then should i just do that?
I believe its safe to say its nothing for sure in the pre-amp stage.
I was thinking to start just replacing some components. This was my list so far.
Would love to know your thoughts and what else i can do/try or should I just start replacing components?
For the cost and if the risk is minimal then should i just do that?
Attachments
Last edited:
Sir Jason . . . . . .Geeeeeeeeeee . . . . .
Here is your markup, it being presented as a circuit board PICK-CHOOR, as it seems you handled it better than a schematic page before.
Your new replacement power transistors are marked up, as per positions, and you must already have them in the right slots and I feel that they will be of the TO-247 configuration instead of the older TO-218 cases, look for the mount hole and if it is a 218 that will be a metal tab with a hole in it, if being the 247 case , that will be having a plastic / polycarbonate tab.
What was being used for heat sink to power transistor insulators . . . . MICA washers . . . . or Gray silicone pads ? ^^^
TESTING . . . .
Lets initially see if the DC voltage drives to the bases of those transistors are being proper, by taking DVM and placing in DC voltage mode and having Negative lead to the 3 GREEN stars common ground connection OR even closer is the GREEN markup of Jumper 50 with its bare wire on the component side or two side by foil lands to either side. The metered point of interest will be the RED circle junction of the shared common connection of the RA18 and RA19 resistors of the OUTPUT transistors emitters.
Upon power up, you should have a negative 38VDC coming into the end of one power transistor and a positive 38VDC coming int the like connection of the other power transistor. Now if all is well in your tied in ancillary transistors, that voltage should balance out and result in cancelling out each others voltage differentials and leaving less than a volt at the RED test point..
If this tests out, then feel free to apply your sine test waveform and aurally monitor on the speaker as you raise the audio level, while keeping an eye on the monitored RED point voltage. Take note of any voltage changes, or, if it only starts showing up as your volume level approaches the onset of distortion that you were previously experiencing. ^^^
Run down the volume now and let's do the same test, using differential mode voltage testing .
The Test points will be the BLUE circles, polarity is irrelevant, one probe on each circle.
Now if you are monitoring those points and have an incoming sine, the NPN output transistor will be responding to the + node of the sine while the PNP will then be responding to the - node of the signal, just after each sines ZERO transition points.
If all is well, the meter will not respond at all. Then as you apply sine and incrementally increase the audio there will either be a negative or positive voltage presence if any imbalanced conditions start showing up, advance on up to, and into your point of distortion ^^^ to see if a DC voltage then starts developing.
Final test will be of the emitter resistor pair, for taking a quiescent static voltage test.
No input audio, just power up and have volume to minimum and one DC voltage meter probe to RED circle and read over to one BLUE RA18 circle and read and log in and then test RED to the other BLUE RA19 circle, expecting the voltages to be the same . . . . and what are the voltages. Expect these readings to be down on in the low millivolts.
If those voltages mate out, your suspicion of any damages to the original BD139 driver and QA BC550C seem to be unfounded.
My PURPLE star reference was just for the need of that transistor to be down in its channel to serve as a heat sink temp sensor.
That's it . . .report your findings. . . . .FIO . . . the ^^^'s markers were just relevant to readings needed to be taken and forwarded for analysis..
BOARDS COMPONENTS LAYOUT / FOIL PATTERN . . . . . vice schematic . . . . .
https://i.imgur.com/U2xLjBX.jpg
73's de Edd
.....
Here is your markup, it being presented as a circuit board PICK-CHOOR, as it seems you handled it better than a schematic page before.
Your new replacement power transistors are marked up, as per positions, and you must already have them in the right slots and I feel that they will be of the TO-247 configuration instead of the older TO-218 cases, look for the mount hole and if it is a 218 that will be a metal tab with a hole in it, if being the 247 case , that will be having a plastic / polycarbonate tab.
What was being used for heat sink to power transistor insulators . . . . MICA washers . . . . or Gray silicone pads ? ^^^
TESTING . . . .
Lets initially see if the DC voltage drives to the bases of those transistors are being proper, by taking DVM and placing in DC voltage mode and having Negative lead to the 3 GREEN stars common ground connection OR even closer is the GREEN markup of Jumper 50 with its bare wire on the component side or two side by foil lands to either side. The metered point of interest will be the RED circle junction of the shared common connection of the RA18 and RA19 resistors of the OUTPUT transistors emitters.
Upon power up, you should have a negative 38VDC coming into the end of one power transistor and a positive 38VDC coming int the like connection of the other power transistor. Now if all is well in your tied in ancillary transistors, that voltage should balance out and result in cancelling out each others voltage differentials and leaving less than a volt at the RED test point..
If this tests out, then feel free to apply your sine test waveform and aurally monitor on the speaker as you raise the audio level, while keeping an eye on the monitored RED point voltage. Take note of any voltage changes, or, if it only starts showing up as your volume level approaches the onset of distortion that you were previously experiencing. ^^^
Run down the volume now and let's do the same test, using differential mode voltage testing .
The Test points will be the BLUE circles, polarity is irrelevant, one probe on each circle.
Now if you are monitoring those points and have an incoming sine, the NPN output transistor will be responding to the + node of the sine while the PNP will then be responding to the - node of the signal, just after each sines ZERO transition points.
If all is well, the meter will not respond at all. Then as you apply sine and incrementally increase the audio there will either be a negative or positive voltage presence if any imbalanced conditions start showing up, advance on up to, and into your point of distortion ^^^ to see if a DC voltage then starts developing.
Final test will be of the emitter resistor pair, for taking a quiescent static voltage test.
No input audio, just power up and have volume to minimum and one DC voltage meter probe to RED circle and read over to one BLUE RA18 circle and read and log in and then test RED to the other BLUE RA19 circle, expecting the voltages to be the same . . . . and what are the voltages. Expect these readings to be down on in the low millivolts.
If those voltages mate out, your suspicion of any damages to the original BD139 driver and QA BC550C seem to be unfounded.
My PURPLE star reference was just for the need of that transistor to be down in its channel to serve as a heat sink temp sensor.
That's it . . .report your findings. . . . .FIO . . . the ^^^'s markers were just relevant to readings needed to be taken and forwarded for analysis..
BOARDS COMPONENTS LAYOUT / FOIL PATTERN . . . . . vice schematic . . . . .
https://i.imgur.com/U2xLjBX.jpg
73's de Edd
.....
Last edited:
OK test results.
Test #1
Negative to J50
Positive to red circle on RA19
DMM set to 20 DCV
Reading = 0.02
Negative to J50
Positive to red circle on RA18
DMM set to 20 DCV
Reading = 0.02
1K sine wave test
Low volume, reading = 0.02 to RA18
Point of distortion = 0.60 -> 1+
If I totally crank the amp I start to hear a voltage hum (I think) as the meter goes up.
Video Link: https://photos.app.goo.gl/Bya5TSMYmPeom5Y03
Test #2
Voltage started at -0.07 at RA18 and 0.11 at RA19
Video Link: https://photos.app.goo.gl/Bya5TSMYmPeom5Y03
Test #3
DMM set to 20 DCV
Probe on RA19 (blue and red circle)
Voltage: 0.09
No input or audio passing through.
Probe on RA18 (blue and red circle)
Voltage: -0.08
No input or audio passing through
Excited to hear your thoughts.
Test #1
Negative to J50
Positive to red circle on RA19
DMM set to 20 DCV
Reading = 0.02
Negative to J50
Positive to red circle on RA18
DMM set to 20 DCV
Reading = 0.02
1K sine wave test
Low volume, reading = 0.02 to RA18
Point of distortion = 0.60 -> 1+
If I totally crank the amp I start to hear a voltage hum (I think) as the meter goes up.
Video Link: https://photos.app.goo.gl/Bya5TSMYmPeom5Y03
Test #2
Voltage started at -0.07 at RA18 and 0.11 at RA19
Video Link: https://photos.app.goo.gl/Bya5TSMYmPeom5Y03
Test #3
DMM set to 20 DCV
Probe on RA19 (blue and red circle)
Voltage: 0.09
No input or audio passing through.
Probe on RA18 (blue and red circle)
Voltage: -0.08
No input or audio passing through
Excited to hear your thoughts.
Sir Jason Geeeeeeeee . . .
Your supplied numbers tell us that you definitely have problems in your biasing and drive circuitry.
The unit is going into full clipping very early on with that applied audio test signal.
Just as preliminary, yet using thorough testing protocol, lets test the supply resistors in the base feed circuitry that could even possibly burn.
That situation usually went out with the use of molded carbon composition resistors of the 1940-60's .
Spot check the resistances being read by the series string of resistors below :
RA1---- 12 ohms
RA4----680 ohms
RA3----270ohms
RA9----12 ohms
RA10---47 ohms
Next point of interest would be the fact that you mentioned the leads associated with the QA-2 BC550C small signal transistor.
Is that unit being the original unit or a different one . . . . AND . . . . if it was pulled, and reinstalled, could it have been installed 180 degrees in error ?
Is the BD139 the original unit also ?
Last interest would be the pulling and testing of the base to emitter and the base to collector junctions of both of those units.
SAFEST PROCEDURE . . . . . to preclude any foil damage or delaminating from board..
Place the chassis so that pcb plane will be flat and facing up
Apply fresh 60-40 rosin core solder to one of the three connections of a transistor and get the old solder and your new solder mixing and keep adding solder until you get a BB sized round blob, move on to the next lead of the transistor and do same and end up with the third lead also having its blob. On the small transistor it's permissible for the blobs to join.
Since . . . . . you will now grab the case of the 550 transistar and start an extraction pull on it, while you rapidly move a WELL TINNED solder tip between the 3 blobs sequentially, until the leads free and the transistor pulls downward and easily flies free.
End result . . .MINIMUM heating time needed, as well as the heat level being transferred to both the transistor and the foil.
Same procedure on the BD139, but it needs longer heating time and more heat. Plus, confirm that the leads are not folded over and will easily pull straight down, even though its flat case is set at 90 degrees to its leads passing thru the 3 board holes.
Use diode test mode on DVM and expect in the 500-700 millivolts range for each of the two B to E and B to Coll junctions..
Additionally, then do a precautionary, C-E test with the two polarity possibilities of the test probe leads.
Transistor Basing Referencing . . . . .
73's de Edd
.....
Your supplied numbers tell us that you definitely have problems in your biasing and drive circuitry.
The unit is going into full clipping very early on with that applied audio test signal.
Just as preliminary, yet using thorough testing protocol, lets test the supply resistors in the base feed circuitry that could even possibly burn.
That situation usually went out with the use of molded carbon composition resistors of the 1940-60's .
Spot check the resistances being read by the series string of resistors below :
RA1---- 12 ohms
RA4----680 ohms
RA3----270ohms
RA9----12 ohms
RA10---47 ohms
Next point of interest would be the fact that you mentioned the leads associated with the QA-2 BC550C small signal transistor.
Is that unit being the original unit or a different one . . . . AND . . . . if it was pulled, and reinstalled, could it have been installed 180 degrees in error ?
Is the BD139 the original unit also ?
Last interest would be the pulling and testing of the base to emitter and the base to collector junctions of both of those units.
SAFEST PROCEDURE . . . . . to preclude any foil damage or delaminating from board..
Place the chassis so that pcb plane will be flat and facing up
Apply fresh 60-40 rosin core solder to one of the three connections of a transistor and get the old solder and your new solder mixing and keep adding solder until you get a BB sized round blob, move on to the next lead of the transistor and do same and end up with the third lead also having its blob. On the small transistor it's permissible for the blobs to join.
Since . . . . . you will now grab the case of the 550 transistar and start an extraction pull on it, while you rapidly move a WELL TINNED solder tip between the 3 blobs sequentially, until the leads free and the transistor pulls downward and easily flies free.
End result . . .MINIMUM heating time needed, as well as the heat level being transferred to both the transistor and the foil.
Same procedure on the BD139, but it needs longer heating time and more heat. Plus, confirm that the leads are not folded over and will easily pull straight down, even though its flat case is set at 90 degrees to its leads passing thru the 3 board holes.
Use diode test mode on DVM and expect in the 500-700 millivolts range for each of the two B to E and B to Coll junctions..
Additionally, then do a precautionary, C-E test with the two polarity possibilities of the test probe leads.
Transistor Basing Referencing . . . . .
73's de Edd
.....
Hey! so ill answer what I can while i'm at work.
First part, can i test those resisters in circuit or do i need to remove them and test each?
BC550C was replaced. I assume the new one was put in correct but I guess I may need to triple check? would anything work if it was backwards?
BD139 was never replaced. its orignal. However, when my friend replaced both power trans. and BC550C the situation occurred where the leads for BC550C were too long and shorting out on the metal chassis.
BD139 they said was getting really host (measured with a heat gun)
So should i pull both these transistors and run the diode test as described?
First part, can i test those resisters in circuit or do i need to remove them and test each?
BC550C was replaced. I assume the new one was put in correct but I guess I may need to triple check? would anything work if it was backwards?
BD139 was never replaced. its orignal. However, when my friend replaced both power trans. and BC550C the situation occurred where the leads for BC550C were too long and shorting out on the metal chassis.
BD139 they said was getting really host (measured with a heat gun)
So should i pull both these transistors and run the diode test as described?
BC550C was replaced . . . . would anything work if it was backwards?
The exact problem which you are now experiencing could be the fault of a mis installed 550 or that past short having blown its emitter junction open.
Feel free to initially try all tests in circuit, but if you find a large resistance error, expect to lift one resistor lead out of circuit to test.
On the transistors you know that you have a bad unit, if a base to emitter or base to collector junction is not present.
The exact problem which you are now experiencing could be the fault of a mis installed 550 or that past short having blown its emitter junction open.
Feel free to initially try all tests in circuit, but if you find a large resistance error, expect to lift one resistor lead out of circuit to test.
On the transistors you know that you have a bad unit, if a base to emitter or base to collector junction is not present.
Would it hurt if i just swapped the BC550C backwards and tested?
Do i need to pull the trans. before i can do any DMM testing?
Here are my resister findings in circuit.
RA1---- 12 ohms -> actual 12.4
RA4----680 ohms -> actual 590
RA3----270ohms -> actual 264
RA9----12 ohms -> actual 12
RA10---47 ohms -> actual 47
I have added more pictures to the google photo share link.
Should i pull the big trans. as well?
Do i need to pull the trans. before i can do any DMM testing?
Here are my resister findings in circuit.
RA1---- 12 ohms -> actual 12.4
RA4----680 ohms -> actual 590
RA3----270ohms -> actual 264
RA9----12 ohms -> actual 12
RA10---47 ohms -> actual 47
I have added more pictures to the google photo share link.
Should i pull the big trans. as well?
Clarify this . . .
Would it hurt if i just swapped the BC550C backwards and tested?
If you mean inverting its collector and emitter leads and powering up ?
Relatively . . . . .
Would it be OK to plunge an ice pick into your eye?
Would it be OK to install your car battery + and - cables backwards ?
Should i pull the big trans. as well?
If meaning the outputs ? . . .they are fine . .. .
Your resistors are fine.
I have added more pictures to the google photo share link.
I don't believe that link was ever given ?
Would it hurt if i just swapped the BC550C backwards and tested?
If you mean inverting its collector and emitter leads and powering up ?
Relatively . . . . .
Would it be OK to plunge an ice pick into your eye?
Would it be OK to install your car battery + and - cables backwards ?
Should i pull the big trans. as well?
If meaning the outputs ? . . .they are fine . .. .
Your resistors are fine.
I have added more pictures to the google photo share link.
I don't believe that link was ever given ?
Last edited:
Fair! hahaha
Here is the link.
https://photos.app.goo.gl/Bya5TSMYmPeom5Y03
by the way. what role does the BC550C play? its not responsible for audio signal amplification right?
Here is the link.
https://photos.app.goo.gl/Bya5TSMYmPeom5Y03
by the way. what role does the BC550C play? its not responsible for audio signal amplification right?
Ok i de-soldered both trans. and tested. Here are the results.
BD139 Diode Test
B (red lead) to E (black lead) -> .673
B (red lead) to C (black lead) -> .671
C to E -> 1
E to C -> 1
BC500C Diode Test
B (red lead) to E (black lead) -> .719
B (red lead) to C (black lead) -> .713
C to E -> 1
E to C -> 1
Added a quick photo of my DMM settings and the BC550C in a clamp.
https://photos.app.goo.gl/iGgP6jS5ALmKIwH43
BD139 Diode Test
B (red lead) to E (black lead) -> .673
B (red lead) to C (black lead) -> .671
C to E -> 1
E to C -> 1
BC500C Diode Test
B (red lead) to E (black lead) -> .719
B (red lead) to C (black lead) -> .713
C to E -> 1
E to C -> 1
Added a quick photo of my DMM settings and the BC550C in a clamp.
https://photos.app.goo.gl/iGgP6jS5ALmKIwH43
