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Sansui AU 4400 Problems, help/advise needed

Spent some time trying to identify any shorts and while measuring from heat sink to TR bolt holes on PCB F 2402 I found TR15 shorted to the heatsinks (6.36 M ohm), T13 and14 open and TR16 at 1.94 M ohm. The heat sink is easy to pull if you agree its issue. Speakers are chaos and read 10.5 ohm. Mica on TR14 showed damage.
 
Pulled heat sink and values differ but board collector bolt holes still show continuity to case ground. Finally seeing ground wires at tr 15 and 16 to case ground and I think heat sink is ok. TR08 is better exposed with heat sink removed so I think I'll pull and test it later.
 
Pulled TR08 and it does meter bad. All readings are OL except neg B to pos C. should read OL but reads 0.680. It is a 2SC711E. I haven't tried to locate one yet. It may not be a big deal to fix but the trace that solders to the C pin lifted from the board. The final 3/4 of an inch pulled away from the board complete with the circular pin hole. it is undamaged but will not lay flat to the board. will look for videos to repair. Not sure about pulling more components before I fix what I have torn apart. LOL
 
dedmonson said:
I found TR15 shorted to the heatsinks (6.36 M ohm), T13 and14 open and TR16 at 1.94 M ohm
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M ohms isn't a short, are TR13 and 14 open on all junctions?

dedmonson said:
Speakers are chaos and read 10.5 ohm
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Sounds good then, maybe they are rated as 12 ohm speakers.

dedmonson said:
Mica on TR14 showed damage.
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Do you think this damage could have been bad enough to allow the collector to contact the heatsink?

dedmonson said:
Pulled heat sink and values differ but board collector bolt holes still show continuity to case ground. Finally seeing ground wires at tr 15 and 16 to case ground and I think heat sink is ok
Click to expand...

Sorry, not too sure what you mean here?

dedmonson said:
Pulled TR08 and it does meter bad. All readings are OL except neg B to pos C. should read OL but reads 0.680. It is a 2SC711E.
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A good transistor should pass voltage in two out of the six way test with your meter. In regard to the lifted trace you could apply a small amount of super glue and stick it back down, trouble is the glue may well lift again when you heat the joint for re soldering. Try a small amount of glue and let set, then expose the trace copper by scraping off the green coating approx 5mm back from solder pad. When you fit the replacement transistor leave the lead for that hole a little long and bend over onto newly exposed trace (this will help to keep it down) and then solder the pad and exposed trace, if you do it quickly the glue may stay intact.

BTW TR08 l assume is mounted to the heatsink and this will be your output temperature tracking transistor for the bias circuit.
 
No indication that TR08 shorted against HS, and it is indeed mounted to HS. Center leg, closest to HS is insulated with tubing. Indications are that NTE85 may be the best replacement for TR08. 2SC1445's came in today's mail. Bad news is I suspect they're counterfeit. The silk screen print looks good but the size differs. Also the underside has a difference in construction ie there is a 1/4 inch diameter circle stamped/crimped on the original C1444's absent on the 1445's.I am reluctant but tempted to report this activity to e-bay. Gluing the trace sounds doable. In the process of watching trace repair videos, it became clear that I have, to date, 7 damaged pads. Two of those pads are as much as 2/3 gone and 5 about 50% gone. Is it possible that point-to-point wiring is more practical than pad replacement? Still having fun but I'm nearing the apex of my ability. Lastly, would you suggest replacements for the C1444?
 
dedmonson said:
No indication that TR08 shorted against HS, and it is indeed mounted to HS. Center leg, closest to HS is insulated with tubing. Indications are that NTE85 may be the best replacement for TR08. 2SC1445's came in today's mail. Bad news is I suspect they're counterfeit. The silk screen print looks good but the size differs. Also the underside has a difference in construction ie there is a 1/4 inch diameter circle stamped/crimped on the original C1444's absent on the 1445's.I am reluctant but tempted to report this activity to e-bay. Gluing the trace sounds doable. In the process of watching trace repair videos, it became clear that I have, to date, 7 damaged pads. Two of those pads are as much as 2/3 gone and 5 about 50% gone. Is it possible that point-to-point wiring is more practical than pad replacement? Still having fun but I'm nearing the apex of my ability. Lastly, would you suggest replacements for the C1444?
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dedmonson said:
No indication that TR08 shorted against HS, and it is indeed mounted to HS. Center leg, closest to HS is insulated with tubing. Indications are that NTE85 may be the best replacement for TR08. 2SC1445's came in today's mail. Bad news is I suspect they're counterfeit. The silk screen print looks good but the size differs. Also the underside has a difference in construction ie there is a 1/4 inch diameter circle stamped/crimped on the original C1444's absent on the 1445's.I am reluctant but tempted to report this activity to e-bay. Gluing the trace sounds doable. In the process of watching trace repair videos, it became clear that I have, to date, 7 damaged pads. Two of those pads are as much as 2/3 gone and 5 about 50% gone. Is it possible that point-to-point wiring is more practical than pad replacement? Still having fun but I'm nearing the apex of my ability. Lastly, would you suggest replacements for the C1444?
Click to expand...
 
If I've managed to get the 2. attached, they are of the TR,s, new and old, side by side. On the left are front and back of the original S1444's. On the right is the C1445's I just boughton e-bay. They illustrate the differences I noted in a my previous post. I would very much like to use them but I dare not without some assurance that they're genuine. The seller has fully refunded, no questions asked. Of the half dozen equivalent TR's I've tried to source they're unavailable. Reading reviews, I'm equally unsure what parts supplier to trust. But once found I'll order TR's o8, 10, 12 and 13 thru 16. We would often say in the Navy, "it's not a job, it's an adventure". Likewise, this project has become an adventure !!!20190404_135637~2.jpg 20190404_135337.jpg 20190404_135637~2.jpg 20190404_135337.jpg 20190404_135637~2.jpg 20190404_135337.jpg
 
Hi mate, sorry l have been a bit busy. In regards to those outputs l wouldn't trust them to be honest, l am glad to hear you got a refund no worries. I would use TO-220's as originally discussed.

TIP41C's would work fine, you cut off the centre pin (collector) then bend the other two down (base & emitter) at a right angle to go through the original holes in the heatsink and into the connector on the other side, bend them so as they are centred in the heatsink hole. Then use one of the original mounting bolts to mount the TO-220 tab (the tab is now the collector connection).

Orientate the TO-220's so as the base and emitter pins locate the same connections as with the original TO-66's.

Use a small piece of heat shrink on the leads and the mounting bolt, only in the small area where they pass through the heatsink.

http://audiokarma.org/forums/index.php?threads/output-transistors-on-an-au3900-what-to-do.508222/

When l get a chance later l will cross reference those other transistors for you. Only buy the transistors from Mouser or Digikey :thumbsup:

In regards to repairing the traces you would be better off laying down a portion of old clipped off component lead (approx 1mm diam). Make a little loop to go around component lead to sit flush with board then on trace end scrape of the coating all along and 5mm into where you find the trace still intact. Then with exposed trace and new clipped lead laying down flat on top solder along the whole area.
 
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No need to apologize for being busy my friend !!! Your time and kind advice is a gift and I trust I'm not taking advantage. Have registered with the Mouser site and will soon make an order. The NTE85 to replace the C711 seems largely unavailable too. Enjoyed reading the link you sent as well.
 
Here are the subs.
2SA726 to KSA992fta
2SC711 to KSC1845fta
2SC1211 to KSC2383ota or KSC2316yta (even better)
2SA697 to KSA1013ota or KSA916yta (even better)

You will have to watch the pinouts on these when fitting as some are different to the originals.
 
You are most certainly not taking advantage, as l said earlier l am more than happy to help. You will find all of the above parts at Mouser. Don't bother with that NTE rubbish.
 
@dedmonson I have a silver faced AU4400 that I got off an AK member @jami w. years ago. The cosmetics are beautiful, but the electronics are a mess. An earlier owner removed the mic circuits (if I remember correctly) and I watched a resistor flame out, etc.

I always hung on to it because it was so beautiful, never wanted to part it out. I would be happy to send it to you for parts for the price of shipping. Hopefully, you'll make good use of it.

IMG_1608.JPGIMG_1609.JPG
 
HepcatWilly: when you have a moment to read this rather long thread, you may better see: 1 my seriously lacking skill/knowledge set. 2 the extreme generosity of Oldsansui441 and thirdly, a clearer idea of the amp problems. To date, TR08 has been proven bad and 3 others are suspect. There also trace and pad issues to overcome on PCB F 2402, I also plan to replace the output TR's. The pics you posted show the original 2SC1444 outputs and an intact G 2404 board. I am located in Indiana, USA. If postage is not prohibitive I am very much interested in your kind offer.
 
@dedmonson Looks like a large flat-rate box from USPS is 19.95 to zip code 46226.
If you want to do this, send me a direct message with your mailing address.

The outputs are original, I do recall there was problems/missing electronics on one of the boards (the mic signal path was entirely removed, if I remember, indicating there was problems in the past).

I hope you can use the original parts and get the system working to your expectations! If this doesn't sound worthwhile, I fully understand and wish you the best.
 
Correct zip is 47446 which probably won't matter. More than willing to send money for shipping. not sure how to "direct message" you. Should I be hesitant about posting personal info in this thread?
 
That is a very kind offer from HepcatWilly, you might be able to use the entire amp board, just desolder the wires underneath. Are you using a solder sucker to remove old component solder? You might find it easier and also kinder on the traces to use solder wick (desoldering braid).

https://au.mouser.com/ProductDetail/Menda/Q-E-5AS?qs=sGAEpiMZZMuzEnlwMwYUNuvIiJbMqHS4M4Lr2vLRB2ckz6QUhFB6dg==

To send a private message just go to the top RH corner of page and click inbox, then start a new conversation and add the necessary recipient. You can ask one of the moderators to remove your last post with your email details if you would like?
 
Oldsansui441: Kind offer indeed. I used a sucker but now have wick and wondered if iron was too hot for too long and too much suction could be causing pad issues. HepcatWilly wanted me to direct message him, but I don't know what that is. Posted my e-mail and hoping we can get shipping worked-out ASAP. I'm excited at the prospect !!! Thanks for another helpful link.
 
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