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Before I Rebuild 1080 Protection Board

T

TinCanAlley

Duck, you sucker!
Subscriber
Okay, I have two issues and I need some input before I just jump in and replace parts....

The first issue I have is when shutting down the 1080. Upon flipping the switch, the lights go out, then the FM indicator light lights up and goes out along with the click of the relay. The unit powers up fine and I have recapped and done a number of transistors, resistors and such a few years back and set the offset, etc. I never noticed it before, but I'm sure the FM light isn't supposed to flash when the relay clicks on powering down.

Second is the volume. I've clean it with Deoxit and followed up with fader lube, but in order to get the left channel to play, I have to bring it up 3 notches before it kicks in. All the while the right is playing from the first notch. Once it is there, I can bring it down and it still plays. If I bring it all the way down, I have to bring it up a few to get it to kick back in. DC offset and bias are set to service manual values. So I'm not sure if it is the volume pot or somewhere in the chain.

The protection board is the only board I haven't touched. I was meaning to years ago, but didn't have replacement relays and started researching if I needed to replace them and one thing lead to another and I never got around to it. I will be doing the board, but need to know if the relays are a must.

Thanks
 
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The description of an audio channel missing until the volume is turned up is a classic indication of a possible bad protection relay contact. While it may be possible to burnish the contacts, that is only a temporary fix. The real fix, if it is the relay contact, is to replace the protection relay.
IMHO the protection relay is a must! The soft-start relay does not carry audio signals, but since you will be in there anyway . . .
Anyway, the transistors and electrolytic caps on the protection PCB should get a refresh. The relay driver, Q2 2SC1438, is notorious for getting tired.
 
After the recap, check the stereo lamp operation again, it has probably to do with the sequencing of the power decay, and that's all random'ed up by the old caps.
 
This great input. So what I'm reading is.... I should recap the protection board as well as replace the relays. Is there anything else on the board that should be replaced while I'm there?
 
markthefixer said:
After the recap, check the stereo lamp operation again, it has probably to do with the sequencing of the power decay, and that's all random'ed up by the old caps.
Click to expand...

I blame myself for not doing this board when I did the all others. I meant to, but didn't have the relays and said I'd go back to do it and never did.
 
merlynski said:
The description of an audio channel missing until the volume is turned up is a classic indication of a possible bad protection relay contact. While it may be possible to burnish the contacts, that is only a temporary fix. The real fix, if it is the relay contact, is to replace the protection relay.
IMHO the protection relay is a must! The soft-start relay does not carry audio signals, but since you will be in there anyway . . .
Anyway, the transistors and electrolytic caps on the protection PCB should get a refresh. The relay driver, Q2 2SC1438, is notorious for getting tired.
Click to expand...

Is this part number the proper one "LY1F-DC48"?

Thanks
 
merlynski said:
I would say yes it is, as it comes up in MTF's list in the reference thread.
I go to this thread for relay selection: Pioneer SX-1010, 939, 838, et.al., Relay Replacement | Audiokarma Home Audio Stereo Discussion Forums,
two options from post #30:
653-my2-02-dc48, $11.25
653-LY1F-DC48, $10.50

Both of these show in stock at Mouser as I post this.
Click to expand...

Maybe I'm too tired, but I looked at both on Mouser and can't see a difference. Is one better than the other, they are the same or do I need one of each (I don't think this one applies)? I'm attaching a pic of my board.

Thanks1080 internals (11).JPG
 
merlynski said:
The description of an audio channel missing until the volume is turned up is a classic indication of a possible bad protection relay contact. While it may be possible to burnish the contacts, that is only a temporary fix. The real fix, if it is the relay contact, is to replace the protection relay.
IMHO the protection relay is a must! The soft-start relay does not carry audio signals, but since you will be in there anyway . . .
Anyway, the transistors and electrolytic caps on the protection PCB should get a refresh. The relay driver, Q2 2SC1438, is notorious for getting tired.
Click to expand...

Of course I'm going to replace the caps based on the values of the originals, but I was noticing when going over the recap lists and the service manual that there should be 6 electrolytic caps on the board. I have 4, and since I see no solder blobs, I'm assuming there are none on the other side. So there must be different revisions of the board with different components.

Do you know a good source for the replacement for the 2SC1438? I can't seem to located it at any of the major places. I'd like to get them from Mouser along with the relays. Also, the 2SA733 is out of stock at Mouser.

Oh, and if you look at the pic of the protection board I posted, does the one lead of the thermal fuse look like it got really hot? If so, I wonder if it was the soldering process or at one point it got really hot.
 
markthefixer said:
After the recap, check the stereo lamp operation again, it has probably to do with the sequencing of the power decay, and that's all random'ed up by the old caps.
Click to expand...

Since you're the expert here.... My protection board has half the number of resistors, 2 less caps and no diodes. It is AWM-120-A (SZC). I'm assuming this makes it an earlier version? Is there anything that could benefit from an upgrade?

Also, what would you replace the 2SC1438 with? I'm having trouble finding the proper replacement for my application, let alone trying to find anything on Mouser. I did find someone selling to NOS on ebay, but I don't think 12.50 for 2 is reasonable.
 
2SC1384 gets replaced with 512-KSC2690AYS, from Mouser, 63¢ if you buy one, 50.3¢ each if you buy ten. Its a TO-126 instead of a TO-92. The leads are a bit thicker, I drill the holes manually with a 1mm drill bit in a pin vise.
 
merlynski said:
2SC1384 gets replaced with 512-KSC2690AYS, from Mouser, 63¢ if you buy one, 50.3¢ each if you buy ten. Its a TO-126 instead of a TO-92. The leads are a bit thicker, I drill the holes manually with a 1mm drill bit in a pin vise.
Click to expand...

So no -92 replacement. I can ream the holes a bit bigger, but I'd rather not if I don't have to. I have days where bad luck finds me.
 
The KSC2690 has been the replacement choice in that application on AK for a long time. The difference in hole size is so small you probably cannot even see it, and I have seen people install the KSC2690 without drilling the holes, drilling just makes it easier. If you really want a TO-92 try a KSC2383. It is actually a TO-92L package, and but has twice the Vce(sat) max (1.5v) as that of the KSC2690 (0.7v).
You unit, your choice.
 
With a 1.5V Vce sat and the relay draw at say 100mA, you only have 150mW of Pd on a part rated for 900mW at 25C ambient
Look at figure 4 on the ksc2383, for 100mA Vce sat is 60mV with Ic/Ib = 10, so it is fine to use without worry, so is 2sc1384 the old work horse.

I use a small drill bit and turn it by hand to open up a hole for a TO-126 if needed
The 2sc1384 is a very low Vce bjt too, I think it is even lower than KSC2383
 
The datasheet I have for the 2SC1384 shows a Typical Vce(sat) of 0.2Vdc, and a Max of 0.4Vdc.
FWIW, it too is a TO-92L package so a KSC2383 will have the same appearance as the original, if that is of concern.
Datasheets attached FYI.
 

Attachments

merlynski said:
The KSC2690 has been the replacement choice in that application on AK for a long time. The difference in hole size is so small you probably cannot even see it, and I have seen people install the KSC2690 without drilling the holes, drilling just makes it easier. If you really want a TO-92 try a KSC2383. It is actually a TO-92L package, and but has twice the Vce(sat) max (1.5v) as that of the KSC2690 (0.7v).
You unit, your choice.
Click to expand...

Cool. I order them and I ordered a bit kit with the pin vise. Hopefully all will arrive by Friday so I can take it down and do the rebuild over the weekend.
 
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