Marantz 2220b Dead right channel

[goodshelac]

I believe those are STV-3H Diodes and not transistors.

https://audiokarma.org/forums/index.php?threads/varister-thermister-diode-question-stu-3h.915710/

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They are pretty rare . . .
These may work, on ebay from Germany:
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Are you sure yours are bad? There are some threads on here about people who have made "work arounds" to replace them as well.[/QUOTI

Well I put my DMM on them and got a .55 reading. and a zero reading the other way around. So I think they are good. The service manual mentions checking these two in particular for troubleshooting a bad channel. The diodes on H705/706 seem like they are out of my skill set unless I find an exact matching sub I'll have to research that a bit more once I start replacing parts. I should be able to start on this Saturday I hope.[/QUOTE]

 

[fromnowon]

The leads on those STV-3Hs are very fragile so be careful when moving them around. They can break off really easily!

 

[Steven Tate]

Those are bias tracking diodes. They are attached to the heat sink and have particular properties related to temperature that keep the bias in bounds as the components heat up. Otherwise, when you set bias, it would rise continuously as the unit heated up.

 

[goodshelac]

Interesting. Will you please post back with how it works and fits?

Actually the one I was planning to try (with stand-offs and wires) is MY2F-DC24

Ok. So here's where I'm at. I've got all of the caps and transistors replaced. My last bit is to replace the blob diodes on H705/706. I'll do this by fusing two small glass diodes together to make a double diode.

As far as the relay goes, I found out that the opaque smaller relays were oddball units and as you stated do not have a modern replacement. I'm not sure I have the skills to try and engineer the MY2F-DC24 into my board. I did remove the old relay from the board and outer case, gave it a deox bath. We'll see.

One question I have is if I am getting idle current at the test points on the amp board but I'm not getting DC on the right channel, can I assume that the issue lies within the amp board? Do the idle current and DC have a direct relation ship with each other in the circuit on that board?

Thank you!!

 

[catrafter]

I kinda doubt that this is your problem as one channel works, but there is a wire from the power supply that feed voltage to the input stages of the power amp module.

Tom

 

[goodshelac]

I kinda doubt that this is your problem as one channel works, but there is a wire from the power supply that feed voltage to the input stages of the power amp module.

Tom

Ok. I did remove that wire to work on the amp board. I've since soldered it back. I'll double check that again.

Are there test points on the supply board that I can measure to the individual outputs, if that makes sense. Want to make sure the phono board, and pre are getting voltage.

 

[goodshelac]

Got everything back in and now the relay won't click on. No power to the board in either channel. Gonna take a break on this for a bit. Not sure what next steps should be.

 

[fromnowon]

noticed this thread with a link to the correct relay for sale:
https://audiokarma.org/forums/index.php?threads/marantz-2220b-not-starting-up.937045/#post-14332388
but that may not be your problem!

Are you going to re-check voltages?

 

[goodshelac]

Thank you for that. I ordered one just to be sure. So...Here's what happened. I got everything back together and was getting no voltage at the board. The unit was powering on, lights and meters working, just no sound and no detectable idle current or DC at the amp board. Then while I was checking I noticed the main power source from the main filter cap (red wire) had broken off the pin. So, I thought well that's an easy fix. Well I didn't give the cap enough time to discharge before trimming the lead and arced it against my wire trimmers. So when I got the wire soldered back on I was still getting no power. Stupid mistake but one I learned from I suppose. The main cap in question was definitely compromised so I ordered a NOS pair I found on that auction site.

Once I get those main caps put in I will recheck voltage. Just got frustrated and had to walk away for a bit.

 

[fromnowon]

This is the relay that I ordered. It is part of a rebuild kit that comes with other caps, diodes, and transistors.

As far as the relay goes, I found out that the opaque smaller relays were oddball units and as you stated do not have a modern replacement.

I think it's unacceptable that a seller supplies a 2220B relay in a kit when it's not going to work on 2220Bs that have the LC relay, without mentioning it. You pay the upcharge vs just ordering yourself because supposedly the parts were picked out carefully. I'd send it back and ask for a partial refund. Or, maybe you can keep it for other projects as that one may work in lots of others. But still.

 

[catrafter]

I think it's unacceptable that a seller supplies a 2220B relay in a kit when it's not going to work on 2220Bs that have the LC relay, without mentioning it. You pay the upcharge vs just ordering yourself because supposedly the parts were picked out carefully. I'd send it back and ask for a partial refund. Or, maybe you can keep it for other projects as that one may work in lots of others. But still.

Unless you tell them, how would the kit seller know which relay is installed?
I don't know what relay is in a 2220B I am sent for restoration until I look inside.

YMMV

Tom

 

[tarior]

I dunno about those kits. Shotgunning semiconductors without an understanding of how they work, what they specifically do in circuit, and which parameters matter is an invitation to an ass ache.

 

[goodshelac]

I think it's unacceptable that a seller supplies a 2220B relay in a kit when it's not going to work on 2220Bs that have the LC relay, without mentioning it. You pay the upcharge vs just ordering yourself because supposedly the parts were picked out carefully. I'd send it back and ask for a partial refund. Or, maybe you can keep it for other projects as that one may work in lots of others. But still.

The seller was apologetic and refunded me the cost of the relay and told me to keep it. It worked out as I'm also working on a 2238b that I think takes the same relay.

 

[goodshelac]

I dunno about those kits. Shotgunning semiconductors without an understanding of how they work, what they specifically do in circuit, and which parameters matter is an invitation to an ass ache.

Perhaps, but for those of us out here that are in the very early stages of learning these processes, it's an easy way to get some practice in. I for one, do not completely understand how to translate a 1977 Marantz parts list to a modern day Mouser equivalent. So if a more experienced person has already done that for me and put together a kit for it, that has value to me in the interim.

 

[tarior]

I have quite a bit of experience, and replace semiconductors only under one of three conditions:
1) Proven faulty
2) Know troublemaker. (VD1212 diode, 2SC458, 2SA726, the list goes on)
3) Mismatched, poor quality, or incorrect device installed during a previous repair attempt by a TV shop.
Just changing out good transistors for the sake of it or because of some perceived need as preventative maintenance is poor practice and can cause a lot of headaches. IMCO.