DLK 1 1/2 Speaker issue

[Jav726]

Hello all,

New guy here. I’ve recently gotten into the audio game and I started with a cap replacement on my DLK 1 1/2s. The originals were 10uf 50V electrolytics with bulging ends. I replaced them with some Dayton PMPC 10uf 250V caps. Installation went well.

I’ve encountered a strange issue where when I turn on the receiver (Sansui 5500) both speakers sound great then the left one goes extremely quiet. There’s a separate issue with the tweeter in the left speaker which I have replacements being delivered to solve. To compound the issue, when I turn my receiver off, the left speaker will emit a loud Pop, followed by a low crackle, before going quiet.

I’ve double checked all my solder points and wires, everything looks fine. Please tell me what I’ve done wrong or how I can diagnose the issue.

Thanks for your help and I appreciate your patience.

[djg]

Sounds like the Sansui is bad. Swap speakers to troubleshoot.

[tom_s]

I love those vintage receivers. I only have two Sansui pieces - a "little" 221 in the shop and a 9090 in storage. Your 5500 has some pretty big electrolytic output coupling caps. C811 in the schematic. The good news is new versions are much smaller and cheaper.

*Important - Measure to see if you have any DC voltage on the output terminals with the volume turned all the way down. You shouldn't see any DC there in a perfect world. Certainly less than a few millivolts if the caps are still good. If it's above 50mv, I would think twice about even connecting any speakers to it. When that caps finally goes, you could have enough voltage on there to fry a woofer. Sadly something of that vintage likely needs to have lots of caps replaced - maybe some transistors too.

[tom_s]

That is a great looking receiver! I just found this page - https://www.vintageshifi.com/sansui-5500-2.php

[Jav726]

That’s what I was afraid of. I switched the speakers and the popping went away for both and remained at the same volume. The receiver has 4 “banks” of stereo inputs, A-D. I left the right speaker on A and moved the left speaker to B. Popping still gone, volume normal, still have the crackling noise in the left speaker after I turn it off.

Safe to assume it’s still the receiver? I may have to send that in for service. Seems a little outside my scope of ability.

[djg]

Do you have any other speakers you can swap in to troubleshoot?

[saabracer23]

Hi, I’ve rebuilt maybe 4-5 dozen Sansui units and most of them have one issue in common. The preamp section is just stuffed with 2SA726 and 2SC1313 transistors. Looking at your service manual I see there are several 2SA726 in there. Pull them, they’re one of the worst transistors ever made. Most that I run into are faulty and noisy after they warm up they start making clicking noises, whooshing noises, etc. They can be replaced with the KSA992 or equivalent. Pay attention to pinout, with the KSA992, you can just turn the transistor 180 to where the flat is facing the opposite way. I also see that there is a fet used in your model 2SK24. Ive run into a few bad ones that resulted in low output of the channel (all dependent on where it is in the circuit). Highly unlikely that is your issue, but no matter what you’ll want to replace the 2SA726. It’s a device known to techs as if you see it, get rid of it. Doesn’t matter if it is currently working or not, it’s trash. If you’re comfortable doing a recap then you should be good to replace those. The transistors will just say “A726” on them.

Dan.

[tom_s]

So reading you're original post again, do you mean the music crackles when you power it down? That's pretty normal - it's just the caps trying power the amp circuit until they are drained down. Or do you mean even with no music playing, you hear a crackling noise? That's not normal, but it could be any number of things.

Does the Sansui have sentimental value?

[tom_s]

Hi, I’ve rebuilt maybe 4-5 dozen Sansui units and most of them have one issue in common. The preamp section is just stuffed with 2SA726 and 2SC1313 transistors. Looking at your service manual I see there are several 2SA726 in there. Pull them, they’re one of the worst transistors ever made. Most that I run into are faulty and noisy after they warm up they start making clicking noises, whooshing noises, etc. They can be replaced with the KSA992 or equivalent. Pay attention to pinout, with the KSA992, you can just turn the transistor 180 to where the flat is facing the opposite way. I also see that there is a fet used in your model 2SK24. Ive run into a few bad ones that resulted in low output of the channel (all dependent on where it is in the circuit). Highly unlikely that is your issue, but no matter what you’ll want to replace the 2SA726. It’s a device known to techs as if you see it, get rid of it. Doesn’t matter if it is currently working or not, it’s trash. If you’re comfortable doing a recap then you should be good to replace those. The transistors will just say “A726” on them.

Dan.

Dan - thanks for that info. I'll file those transistor subs in my Vintage Tech notebook.

[saabracer23]

Dan - thanks for that info. I'll file those transistor subs in my Vintage Tech notebook.

Sounds good, for the 2SC1313 you can use the KSC1845. The 2SA725 and 2SC1312 are also junkers and can be replaced with the same transistors I suggested, but don’t see those as often.

Dan

[Jav726]

So reading you're original post again, do you mean the music crackles when you power it down? That's pretty normal - it's just the caps trying power the amp circuit until they are drained down. Or do you mean even with no music playing, you hear a crackling noise? That's not normal, but it could be any number of things.

Does the Sansui have sentimental value?

It crackles with or without music. I just tested it on the FM radio with the volume at 0 and it gave a very audible crackle for maybe 2-3 seconds before finally going off.

It has some sentimental value, I’d like to keep this one and fix it if it’s somewhat fiscally responsible. I love how it sounds when paired with these speakers. And I didn’t have any of these issues until after the re-cap, which is why I initially thought it was the speakers giving me trouble.

If I were to go the self-service route, I found this site that sells the 80+ necessary caps as a kit. Does anyone have any experience with this site? If it’s not reliable, I can use the manual to find what I need. Link below.

https://www.audio-high-store.com/pro...io-capacitors/

[tom_s]

It sure sounds like you have a leaking cap or bad transistor in there somewhere. The "fun" part is finding out where. You can wrap a whole lot of time & money into replacing all the caps & transistors on one of these things. I know some warn of going the shotgun approach - replacing everything in one long session. If you do that and have a problem, say the unit doesn't fire up or misbehaves in a new way, you have go over everything you've replaced to find what's wrong. Better to do one board at a time, then make sure it still works before moving to the next one. And sometimes the problem is not where you first suspect. I have a Pioneer SX-535 with low output in the Left phono preamp section. I replaced all the suspect electrolytics, but that didn't fix it. So then I replaced most of the transistors on that board, but the problem persists! I just bought a new scope & signal generator, so I'll get in there and follow the signal to see what I can find. My guess now is a bad small value ceramic cap.

I would be cautious of most bulk rebuild kits. I've been advised there are quite a few fake parts floating around - mostly from overseas. If you have the time to build up a BOM from the service manual, you'll get genuine parts from Mouser or Digikey and probably save a few bucks in the process.

Have you been on Audiokarma? That's a great place for answers to questions about vintage gear. There's even a dedicated Sansui forum. I'm sure somebody there has dug into a 5500. Nice bunch of guys too!

[Jav726]

Ok yeah that’s good advice. I pulled it from the wood case just to see what I’m dealing with. I’ve attached a pic. This just seems overwhelming. I don’t think this has been taken apart since it was manufactured.

[Jav726]

Here’s the bottom plate taken off

[saabracer23]

Ok yeah that’s good advice. I pulled it from the wood case just to see what I’m dealing with. I’ve attached a pic. This just seems overwhelming. I don’t think this has been taken apart since it was manufactured.

Is that it’s current state? I see several capacitors that look original (the grey Elnas). Did you recap the preamp section? It actually isn’t to bad, put it up on its side. Take all of the nuts and screws off of the switches and pots across the face. There will be a couple of screws on either side of the face plate that will allow you to disconnect it from the sides. From there you can get to the preamp boards. There should be two layers. Do the nearest to the bottom first, easy as all of the solder points are right there for you. Once done then move those boards to the side (if you remove the controls from the face you should be able to swing them out of the way) and then go at the second layer.

I see several of those transistors I spoke of earlier, trust me, they will only continue to give you trouble. Where are you located? What tooling do you have? Any good desoldering tools?

Dan

[Jav726]

Yeah those pics were taken today. I’m in the KC area and I have a fairly basic soldering kit. I really think this is outside my wheelhouse. There are several stereo repair shops in the area but their backlog is several months out. I’ll probably just have it serviced at one of the shops and go without it for a while. I really appreciate all of your help.