I've a sick 5500

PaulL

New Member
Hi all. New member here and first post.

I was doing some research on my 5500 looking for information and Audiokarma kept popping up. I’ve read a few of the post in this sub-forum, as well as others, and figured this would be a good place to see if anybody could steer me in the right direction.

The unit in question is a Sansui 5500 that I acquired while stationed in SEA. Bought it from the PACEX catalog and had it shipped straight home. So I’m the original owner.

I had it in storage (boxed and covered) for a few years while using a Sony entertainment system. When it came out of storage there is a lot of static in the left channel. Not really popping, just crackling. Reminds me of an AM radio during an electrical storm.

The noise isn’t immediate, takes about a minute to show up. It is consistent, doesn’t vary with the volume, balance, input, reverse or mono settings. It is also present when using headphones, either jack.

At this point I’m thinking it’s something on the driver board or the final amp for that channel. But I was hoping someone could tell me what to look for and how to find it.

The unit has been serviced before, about 20 or so years ago, but I don’t recall for what. As best I can tell it has the original electrolytic capacitors in the power section as well as coupling capacitors.

I’m digging through the forum looking for a thread that covers this sort of thing, so if it’s already been covered, just point me in the right direction.

Thanks
Paul l
 
I would consider a recap in the medium term due to the units' age.

However the issue you have is most likely a failing small-signal transistor. If you have another amplifier - run the amp in separated mode (switch at the back) run a signal from the pre amp out jacks to your other amp. Then as the next test, run low level music signal in the power amp in jacks (make sure this source has its own volume control!)

Doing this will isolate whether the problem is in the pre or power section.

Clean all your controls with a good cleaner like deoxit first to eliminate dirty contacts being your possible cause.
 
Thanks.
I sprayed the controls before firing it up, but may give them another shot. The row of push buttons are hard to get to.
I have never actually used the channel separation feature, but will give it a try and get back. Finding a source won't be a problem. I'm gonna have to get creative with finding an amp.
 
Hi and welcome to AK

Re the separated test, you can set to separated and the use an RCA cable to swap the channels. Feed left out to right in and vice versa. If the noise moves to the right channel then it is the left pre amp causing the noise. If the noise stays in the left channel then it is the left main amp where the problem is

Cheers

John
 
The separation test leaves the static in the left channel. Looking at the schematic, the pre-main separation switch is before the driver boards. These boards are plug in with edge connectors. Of course these face up to collect as much dust as possible.:(
So I pulled them and tried to clean the card edge and the strip connector they plug into. It didn't help.
Now, these cards are theoretically identical, aside from the bias settings. Would it be safe to swap them to see if the static follows the card?

Paul
 
Before replacing any parts, be absolutely sure the controls are clean. They are the #1 source of "crackling" and low or no sound output issue. The contacts in the controls are very likely oxidized do to the long storage. Start by "exercising" each of them and make note of a control that changes the crackling. To clean them properly, you need to get a cleaning solvent inside the control onto the contact surfaces. I usually takes some disassembly to get access to an appropriate opening on the control. Start with Deoxit D5. The switches may require something stronger. Use electrical contact cleaner that is safe for plastics followed by D5.

Do not start replacing capacitors and expect to fix this problem. Fix the problem first. Otherwise you run the risk of introducing a new issue on top of the original issue. That makes it much more difficult to sort out.

Also, please post the serial number for the database. Click on the link in my signature block.

- Pete
 
Oh, I'm not going to just start recapping the unit just to say I've recapped the unit. I may well replace the major electrolytics, but I would prefer to start with a working amp when I do that.

The data base is requiring a separate sign in and doesn't want to accept my Audiokarma password.
 
Well, the transistors I can read are not 2sc458. However, two of them have heat sinks wrapped around them and can't be read. It would appear from another thread that these were used as the first stage of the board. If that's the case then they were not used here as I can read that one. It's also the only one on the board with that shape of case.

I did switch the boards left to right and the noise followed the board. The good board shows signs of having been repaired. Which was probably from the previous servicing. Two transistors seem to have been replaced, one of which is the first stage. Again, this is on the good board. I'll assume the noisy board is all original.

Any suggestion on how to tell if the same thing happened to this board as happened to the other?

Paul
 
Hi Paul

Prime suspect is the 2SC871 (TR802) at the input of the main amp board. If you have some freezer spray this can be used to diagnose noisy transistors, a quick squirt on the suspect transistor and the noise will either increase or decrease if the suspect transistor is in fact causing the noise.

The 2SC871 is a know noise maker, should be replaced in any event. Use a KSC1845 (and be mindful of any pin out differences)

Cheers

John
 
Thanks John,
2SC871 (tr802) is the transistor that has been replaced in the right channel board. For what it's worth, though, Sansui didn't use 2SC871 in my unit. This board has a C1312 in that position. I don't know if that should be 2SC1312 or not. The right channel main amp board, the one that has been repaired, has a C1345 in the T802 spot. And it's oriented 180 degrees from the left board. Appreciate the heads up on the pin out issue.
Again, thanks, I'll get a can of spray and see what I can find out.

Paul l
 
Oh, I'm not going to just start recapping the unit just to say I've recapped the unit. I may well replace the major electrolytics, but I would prefer to start with a working amp when I do that.
I find the most problematic capacitors are usually the tiny guys! 1uf - 10 uf tend to dry up faster than the large " major " caps. I would just go ahead and replace all the caps but only after you have fixed your problem.... sounds like those transistors
 
I finally got some freeze spray and got back to this unit after a couple of weeks distraction.
This time it came on and played clean for 5 minutes or so, no static. Then the left channel just went out. Silent.

Spraying transistors and capacitors on the driver board produced no effect, so I tried the finals.
There is a .68 ohm 7 watt resistor on the emitters of both transistors. Spraying one brought it back to life for a few seconds. Repeated spraying restored sound each time.

I'm going to lift one lead and check, but I suspect that it'll read OK cold.
Is there anything I should check before replacing that might have caused it to go bad or is this simply old age.
And, should I replace the other identical resistor on that channel.

Paul
 
Should be able to test those in circuit i think? Sounds like emitter resistors, i would test, and if bad replace both
 
I'm gonna revive this thread one more time to say thanks for the help!!
Life got in the way but I finally got the output resistors back in today and the 5500 sounds great.

Again, thanks to all.

Now on to the HH Scott 299f.

Paul
 
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