Sir ssyniu . . . . .
Working with :
OK the SW101 checked and works properly for the right channel
the left is distorting despite / irregardless of / the position of the SW101
and
but I can borrow a multimeter from my friend.
The most that might possibly do is to permit you to leave the record inputs without any input connections , and then you place the DVM in its DC voltage test mode with Black negative probe to ground and then use RED positive probe to test the same circuit points on the Right and Left channels to see if there might be a noticable difference between their voltages.
OR you could test in differential mode, where you place a + lead on one identical circuit point of one channel and the other probe on the same circuitty point on the other channel. THEN if the voltages are being the same, no meter reading will be perceived.
But if there is being a difference in levels, then the voltage difference will be READILY seen.
So . . . . . its confirmed, that the units right channel is the one that is working properly.
If you look at the marked schematic you can see that the signal comes in at the RIGHT input jack at the top right corner and proceeds towards the left, through 4 stages of amplification, until it finally connects to pin 27 of the large IC106 at the far left..
I have maked the three different increasing levels of the audio signal as it passes from the right to the left with Right 1 . . .Right 2 . . .and Right 3 labelings.
The same is being done with the Left channel with its Left 1 . . .Left 2 and Left 3 and its signal passig into pin 2 of that same IC 106.
Now I don't know how that unit was being connected for your testing, with you pushing buttons for changes, as I was expecting two connectors being plugged into those two RIGHT and Left Record input jacks . . . . which they might be, but I don't relate that to the button pushing audio test session.
Additionally, I was expecting a stable 400~ or 1 khz or middle C, audio sine wave test tone instead of that whiz-whomp-bang -whirrr-thump muzik.
BUT if the Left channel is just being dead, instead of having some degree of distortion, I guess that a no audio at all fault, is certainly being detectable.
You certainly will need to find a source of the mentioned range of permissible values of a paper or ceramic or poly cap, that would exhibit almost no degree of DC leakage as an electrolytic capacitor would.
So you need to think of any of any electronics that you have that could supply a salvaging and temporary use of one of those caps.
OR you may have electronics inclined friends that could loan you one, or you buy one from a local supplier or a contact ham radio person, possibly for a freebie.
The clip leads just enable you to clip that capacitor into circuit, with out you having to solder it in.
HOWEVER, considering that you are being a soldering person , two adequate length wire leads, used as exttensions to the caps leads and two end solder connection into solder points in the circuit . . . . would then get your capacitor connected into circuit.
HERE IS YOUR TEST CONCEPT:
You now know that all is being correct with your right channel performance, so we will use it to ADDITIONALLY inject its GOOD audio into specific, like level test points of your quirky Left channel.
You would have an audio input going into the units RIGHT record input jack and, initially, we go way down to its extreme end at marked on R3 test point.
Your Left record input jack, you leave without any thing being plugged into it.
You connect our required capacitor between R3 and L3 test points.
Now when you do a test recording session, the good audio of the RIGHT channel will pass down, just as it always did, but will ADDITIONALLY cross on over, thru the test cap, to also feed its good audio signal, into the A/D input of the IC102 at its pin 2.
If all is well in your test recording session, the right channel should still record good as expected, BUT additionally the Left channel audio should also be good, since it was ACTUALLY being the flawless RIGHT channels audio.
Considering that being a successfull testing, you would then move the test cap from where you had it , to then being between R2 and L2.
Do the same test recording procedure, if it is successful, you then have eliminated Left channels IC 105 as not having a fault.
If all is well, then you move the test capacitor between R1 and L1 to see if 1/2 of IC 104 is being good.
I stop at this point for feed back or any ?'s from you . . . if so being needed .
OBSERVATION . . . .
On your units display . . . the right halfs brightness appears to me, to be appreciably brighter than the left side.
Assuming that incand lamps or LEDS might be used for backlighting illumination, the left side might have an outage.
73's de Edd . . . . .
HEY ! . . . All you AUSSIE fellers . . . . REMEMBER ! . . . . .that in the dreaded Australian outback . . . . anything that doesn't eat you TODAY, is merely saving you for tomorrow.
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