Denon AVR-1912 E2/EA

[Michael Studio1]

Hey, great find!!
I woud download data sheets and compare the missing transistor number(s) with the transistor specified on the print.

Btw, HighB originates on page 108. It looks to be a 7v rail.

Yay. Its exciting to find fried components! Well, that or I'm just a geek.

Fried Transistors (on Toast) I have sourced a pair of the two 'outer' Transistors - they come as: one SK D2390 together with one SK B1560 - free postage from China - for $2.44. That's something to look forward to - by the time it gets to the Russkie nUKed UK it'll be 2L8. Michael Studio1 UK 17:06GMT

 

[Michael Studio1]

I also found a packet of 5 x Toshiba 2SC3964 for $1.88 - which your post suggested according to the Cct.Diag. page107/G7 (Q469) so again we wait the China Post. Michael Studio1 UK 17:12GMT

 

[Tha fios agaibh]

.....And a 40% chance China post looses it.

I would hold off ordering anything until you have a complete list of parts you need.
(Shipping costs would be minimized)

 

[Michael Studio1]

.....And a 40% chance China post looses it.

I would hold off ordering anything until you have a complete list of parts you need.
(Shipping costs would be minimized)

Thanks, John, for your concern and tremendous help in this project. Shipping cost is Nil.. As yet I need no more than those transistors - hopefully this will remain so! but who can tell? Which is why I was commenting on 'Why these Transistors toasted themselves in the first place!' And I still don't know whether the original cause of an interrupted Left Channel has been fixed. But it's been entertaining and instructive so far - so who knows? all may yet be well. I will be in contact when the components arrive. But I am still concerned at the lack of information in the Service Manual relating to those heat-sink mounted components. When all else in that Manual is so artistic, pristine and fully considered it seems extremely strange that those important components were totally ignored. Your most welcome identification of the otherwise un-identified Transistors and their not even being in the Parts List is most extra-ordinary. Michael Studio1 UK 19:22GMT

 

[Michael Studio1]

It occurs to me that with the removal of those three defective Transistors from the AVR it can be re-assembled and tested - or will it not work without a fully functional 7Channel Amp? Michael Studio1 UK 06:51GMT

 

[Michael Studio1]

AND IT DOES! (Turn ON and stay on - senza those three heat-sink mounted Transistors.) That being the case I feel there is no need to await the arrival from China of the new 2SC3964 and (these are coming as a pair) the SANKEN 2SB1560/2SD2390. So I shall go ahead with my Tests. First checking the 6 Channels for Page56 - the Idling Current - is still at 2mV. then re-adjust all 6 Channels to the required 3mV. Then inject different tones into VAUXL and VAUXR and see if they get to FL and FR Spkr Terminals. Yee Ha! Michael Studio1 UK 09:11GMT

 

[Tha fios agaibh]

Great progress.
You could, but I see no urgency with calibrating it right now. Besides, you'll likely have to recalibrate once you put humpty dumpty back together. Also, I wouldn't turn up the pot related to the missing transistors.
Obviously, don't power up any transistor without its heat sink. We don't want any more toast.

Instead, I would take some time to go through the surrounding components such as electrolytic caps, diodes and transistors (if you haven't already) and check their health. Anything with a DC path to your failed transistors could have also taken a hit.

Might want to do some comparisons with known working channels, to the faulty FL channel. Who knows, you may stumble on why it cuts out.

 

[Michael Studio1]

Great progress.
You could, but I see no urgency with calibrating it right now. Besides, you'll likely have to recalibrate once you put humpty dumpty back together. Also, I wouldn't turn up the pot related to the missing transistors.
Obviously, don't power up any transistor without its heat sink. We don't want any more toast.

Instead, I would take some time to go through the surrounding components such as electrolytic caps, diodes and transistors (if you haven't already) and check their health. Anything with a DC path to your failed transistors could have also taken a hit.

Might want to do some comparisons with known working channels, to the faulty FL channel. Who knows, you may stumble on why it cuts out.

Thanks, John. Your input is, as ever, most welcome. There are no Transistors senza heat-sink - so there'll be no toast for breakfast. What I proposed to do was fire up the AVR as though there were no problems, leaving VR106 (SBL) at '0' and to adjust all the other channels to 3mV. This I have done. I then checked, with AGND reference, the Voltages at: CP13A pin7 = +8.159V. then at CP13A pin 6 = -7.815V. and CN14 pin15 = +3.669V. (not good!) finally at CN101 pin1 = +14.2V. (these are my 'TaggedTestTails' so it's easy to check). I have injected 500cps into VAUXL and 700cps into VAUXR. Both tones get to IC801 pin21(FLOUT) and 23(FROUT) but neither are evident at the 7 Channel Amp at CP401 - the 13 core ribbon cable. So I'll just fire up my Pavoni Europiccolino and make myself a LARGE strong frothy coffee. Michael Studio1 UK 11:04GMT

 

[bushtech]

All I can add is have you checked those 470Ω resistors in those lines?

 

[Michael Studio1]

Great progress.
You could, but I see no urgency with calibrating it right now. Besides, you'll likely have to recalibrate once you put humpty dumpty back together. Also, I wouldn't turn up the pot related to the missing transistors.
Obviously, don't power up any transistor without its heat sink. We don't want any more toast.

Instead, I would take some time to go through the surrounding components such as electrolytic caps, diodes and transistors (if you haven't already) and check their health. Anything with a DC path to your failed transistors could have also taken a hit.

Might want to do some comparisons with known working channels, to the faulty FL channel. Who knows, you may stumble on why it cuts out.

Your para. 2. For (SBL) I have checked all surrounding Caps (2) ZD's (2) D's (4) all are healthy and compare to SBR. There's nothing to arouse suspicion. So when the China Slow Boat arrives I shall readily install the new Transistors.

Para 3. I am making a FL > FR Channel comparison test right now. This 7CH AMP slides out just like a honeycomb from a super. (in a bee hive)

In my previous post I mentioned the loss of both signal tones between IC801 pin21(FLOUT) pin23(FROUT) and CN401 - which doesn't make sense as there are no components between these two points. But the tones are very low at IC801 pin21 and pin23 with much background noise. I don't like that +8V. at CN14 pin15 = +3.669V. Michael Studio1 UK 12:53GMT

 

[bushtech]

between IC801 pin21(FLOUT) pin23(FROUT) and CN401 - which doesn't make sense as there are no components between these two points.

Strange, on page 114 of the manual I can see a resistor in each line, R808 and R814

 

[Michael Studio1]

Strange, on page 114 of the manual I can see a resistor in each line, R808 and R814

Thanks, Bushtech - you are right, of course. I had stupidly not seen them and will check them pronto. As for the juicy green resistors in line with the legs of the Power Transistors - I'll check those as well. Thanks for you observations. I'm having the Op. next week (Cataracts) - quite true. Michael Studio1 UK 13:34GMT

 

[Michael Studio1]

R631 a small red METAL.FILM Resistor of approx. 21.7Ω(comparing ones nearby) is OPEN. As are two green resistors R640 and R641 - each of these should have a resistance of 0.47Ω Their colours are: Yellow (around the thick end) Violet, Silver, Brown (though this could be Gold.).Any ideas for sourcing these? Also C515 in the FL Amp. is 'leaky' according to my Peak ESR70 meter. It says it is 47μF 10V. electrolytic. Which could account for the FL Amp. not working? Michael Studio1 UK 15:22GMT

 

[Michael Studio1]

Strange, on page 114 of the manual I can see a resistor in each line, R808 and R814

So I also see (without noticing them!) Thanks, Bushtech. I must find them physically and check them out. Michael Studio1 UK 15:25GMT

 

[bushtech]

0.47Ω resistors: https://eu.mouser.com/Search/Refine.aspx?Keyword=resistor+0.47

 

[Michael Studio1]

0.47Ω resistors: https://eu.mouser.com/Search/Refine.aspx?Keyword=resistor+0.47

Thank you Bushtech. Looking at the Parts List p174 it seems these are 2W (2Watt?) Would you agree? They are available from Mouser up to 5Watt. though in the context of what is required whether one goes up (like Volts in a Capacitor) or tries to get the 2Watt as seems to be specified - I'm not sure. Michael Studio1 UK 19:19GMT

 

[bushtech]

Yep 640 and 641= 2W
631=1W
Try to stick to the same wattage as size wise then the replacements will fit nicely. If they run hot you can then shoehorn a higher wattage replacement in. Having said that I was surprised at how hot they can run quite happily.

 

[Michael Studio1]

Yep 640 and 641= 2W
631=1W
Try to stick to the same wattage as size wise then the replacements will fit nicely. If they run hot you can then shoehorn a higher wattage replacement in. Having said that I was surprised at how hot they can run quite happily.

Thanks, Bushtech, just what (Watt?) I thought. Michael Studio1 UK 20:55GMT

 

[Michael Studio1]

I have just been trawling the net for four 0.47Ω 2w. and, on an eBay offer got 5 for £1.48p. Farnell sells 0.47Ω

All I can add is have you checked those 470Ω resistors in those lines?

Hello Bushtech. Thanks for that question re:SM's R808, R809, R812,R813,R814 + R820 and R821 - This is where I make a 'plug' in favour of getting an 'endoscope'. This enabled me to identify the SM's in the foil connecting to CN401 (page114/O3) All 470Ω resistors in those lines check OK. so where those Signal Tones disappear is unclear. Good point though! I would re-check all this again with the Sig.Gen. (FeelTech FY3200S - a quite inexpensive bit of kit and really worth looking up - considering its features!) but as I have removed the 7Channel Amp with its attached large Heat-sink and have levered up the PCB on it in order to remove that questionable capacitor: C515 on Channel FL, the AVR cannot readily be reassembled for such a test. However I shall now take my UNI-T (model UT-61E) meter which gives a readout on the Lab PC screen - making it another bit of useful kit as the meters' screen is not back-lit. The connector to a PC comes with the meter and terminates in an RS232 'D' type plug for that purpose. Michael Studio1 UK 14:00GMT

 

[Michael Studio1]

Later: I have checked continuity from the relevant IC801 pins (page114) through the SM Resistors to CP401 plug contacts at the end of the 13-way ribbon cable and found all OK. Michael Studio1 14:44GMT