Marantz 2220B (Later '78?) Restoration Advice/Questions

[hhspunter]

Hi all,

I picked up a 2220B a few years ago for dirt cheap and have been using it in the garage ever since. I finally got tired of the scratchy/intermittent controls and decided to do a fairly extensive restoration. I believe this one was built in 1978, and so it does not exactly match the service manual since it has the Dolby board (PC01, which seems to match the 2230B service manual).

At this point I've fully disassembled the chassis and extracted the harness/boards nearly entirely intact to make it easier to work on and clean (it was very dirty inside and there is widespread surface corrosion). I've documented and verified most of the electrolytic caps (still need to do PE01). Also managed to separate the power amp board from the heat sink without harming the thermistors, yay.

In general, I plan to:

• Thoroughly clean all boards, they are covered in dirt/grime, although the bottom sides look brand new
• Address the surface corrosion on the chassis by cleaning/scouring/sanding only if needed, follow-up with zinc-rich primer or something where appropriate
• Clean faceplate, buttons, etc.
• Clean all controls, they are bad (MG 401B, possibly 99.9% IPA soak/flush, Deoxit Fader Lube to finish)
• Clean external contacts (RCA jacks etc.)
• Replace a knobless Dolby switch (post broke off flush)
• New vellum paper
• New incandescent bulbs, maybe replace the white plastic bulb housing since mine is a little melted
• New electrolytic caps (at the very least main filter caps, P400, P700, P800, PE01)
• Re-paste the output transistors
• New output relay
• Replace the wire loom "clampers" (most broke during disassmbly due to being very brittle)
• Replace the push-style binding posts with banana jacks (mine are quite corroded and I have a 3D printer)

I would greatly appreciate any advice, and have some specific questions - I've done quite a bit of "research" and I'm a bit overwhelmed by the varying opinions on these topics over the years:

1. Should I re-cap the radio-related boards? (P100, P200, P300, PC01)
2. Should I replace any transistors? If so, which are the "must-do"?
3. Trying to decide between an eBay kit like this one and piecing together my own kit (I'm a regular user of DigiKey/Mouser)
4. Maybe a can a worms, but I know there are a lot of opinions on exactly which line/model of cap to use where, and I am totally overwhelmed by it - I'm just trying to make this perform closer to "like new" not necessarily trying to make it as good as possible. Any advice appreciated.
5. Should I replace any tantalum caps or any other passives?

A few pictures of the untouched condition of things:

Disemboweled 2220B:

Pretty grungy chassis, but will be easy to clean now:

 

[dankik]

I don't know about your unit, but some have a Cadmium coated chassis. I'm no expert, but as I understand it, Cadmium dust can be hazardous to your health when breathed. Just be careful.

 

[ConradH]

As long as you're in there, replace all the electrolytics with 105C general purpose commercial grade caps, including the RF boards. Alignment shouldn't be sensitive to the caps, though at this age and condition the alignment really needs to be touched up anyway. Replace any tants with equivalent low leakage electrolytics. I'd also replace any small signal transistors that have known problems, like 458s and various others you can find by searching here. If they used any fusible resistors, those tend to rise in value and need to be replaced, usually with plain metal films. Clean and re-grease power transistors- I use higher grade Sil-Pads, rather than grease and mica. IMO, a dust mask and doing the chassis wet is a good idea to avoid toxics. Of course, give the transformer a nice paint job!

 

[ivandezande]

1: Don't use incandescent bulbs! It'll just melt again and they'll just burn out again.
2: Use silpads for the outputs. Cleaner and at 20W you don't have to worry about heat dispersion and can get cheaper pads.
3: Replace all transistors except for in the tuner. You'll benefit from a more reliable unit and a lower noise floor. I've chased too many gremlins down where I do this for every unit now.
4: Replace the trimmers. Use Bourns 3386H series.
5: Replace the emitter resistors. I like to do this as they can break down, are cheap, and arguably an important component.
6: Replace zeners and dual diodes. I do single rectifiers too somedays.

 

[hhspunter]

Thanks for the replies everyone.

1: Don't use incandescent bulbs! It'll just melt again and they'll just burn out again.

I was thinking I'd like to keep the original color - if there are LEDs that can match it that would be great! But it seems like all the options are too cool/blue?

2: Use silpads for the outputs. Cleaner and at 20W you don't have to worry about heat dispersion and can get cheaper pads.

I've already got plenty of thermal compound from PC building but I will look into this option.

Replace all transistors except for in the tuner.

The eBay kit I'm eyeballing comes with a whole bunch, I think I'll start there and fill in anything missing from DigiKey. A couple specific questions though:

• I assume this recommendation includes replacing output transistors? Do they need to be matched?
• I assume I want to match the differential pairs H701-H704?

Replace the trimmers. Use Bourns 3386H series.

For all boards, or just the power supply and main amp boards? Seems like I might do more harm than good replacing on the radio boards?

Replace the emitter resistors.

Do you mean all emitter resistors? Or just the big ceramic cased resistors on output transistor emitters? Or?

 

[ivandezande]

Thanks for the replies everyone.


I was thinking I'd like to keep the original color - if there are LEDs that can match it that would be great! But it seems like all the options are too cool/blue?

I've already got plenty of thermal compound from PC building but I will look into this option.

The eBay kit I'm eyeballing comes with a whole bunch, I think I'll start there and fill in anything missing from DigiKey. A couple specific questions though:

• I assume this recommendation includes replacing output transistors? Do they need to be matched?
• I assume I want to match the differential pairs H701-H704?

For all boards, or just the power supply and main amp boards? Seems like I might do more harm than good replacing on the radio boards?

Do you mean all emitter resistors? Or just the big ceramic cased resistors on output transistor emitters? Or?

Fair, but with warm white LED's and two layers of vellum it's pretty dang close.

Woah woah woah - you better not be using CPU grease. That stuff is conductive and not good in this application.

Yes. Matching doesn't matter. MJ21193/4G or MJ21195/6G, whatever is in stock.

Not on the tuner board. Power supply board 3386F, amp board 3386H.

I mean the output emitter resistors or any other big ceramic resistors.

 

[hhspunter]

I don't know about your unit, but some have a Cadmium coated chassis. I'm no expert, but as I understand it, Cadmium dust can be hazardous to your health when breathed. Just be careful.

Thanks for the heads up! I will certainly be careful, I thought it looked a little different than most zinc coatings...

As long as you're in there, replace all the electrolytics with 105C general purpose commercial grade caps, including the RF boards. Alignment shouldn't be sensitive to the caps, though at this age and condition the alignment really needs to be touched up anyway. Replace any tants with equivalent low leakage electrolytics. I'd also replace any small signal transistors that have known problems, like 458s and various others you can find by searching here. If they used any fusible resistors, those tend to rise in value and need to be replaced, usually with plain metal films. Clean and re-grease power transistors- I use higher grade Sil-Pads, rather than grease and mica. IMO, a dust mask and doing the chassis wet is a good idea to avoid toxics. Of course, give the transformer a nice paint job!

Thanks for the advice!

 

[hhspunter]

Woah woah woah - you better not be using CPU grease. That stuff is conductive and not good in this application.

Thanks for the clarifications! And thanks for the heads up here - the stuff I use is not conductive (though you can get conductive paste) - but I'd still have to use a mica insulator as ConradH mentioned, which would indeed be more of a pain. Looking at it closer now and referencing the datasheet I now see that the case (collector) is connected via the screws that thread into the strap on the backing plate.

 

[fromnowon]

follow-up with zinc-rich primer

Interesting - I didn't know that primer existed. I'm curious what you end up with and how it looks after. I've always just done touch-ups with rust remover and some clear coat, and of course that doesn't look very good (but I figure it at least controls the situation). With it all taken apart like yours, the zinc primer spray might work really well? I'll bet it turns out great. Let us know how it's going!

 

[fromnowon]

I thought of something else @hhspunter - if you haven't come across it yet,
https://audiokarma.org/forums/index.php?threads/marantz-2220b-speaker-relay-replacement.881545/
There are some peculiarities if you plan to replace the relay. From the picture it looks like yours could be the clear type, which is good!

 

[hhspunter]

Interesting - I didn't know that primer existed. I'm curious what you end up with and how it looks after. I've always just done touch-ups with rust remover and some clear coat, and of course that doesn't look very good (but I figure it at least controls the situation). With it all taken apart like yours, the zinc primer spray might work really well? I'll bet it turns out great. Let us know how it's going!

Something like this is what I had in mind. Not as good as hot-dip or electroplating, but better than nothing.

I thought of something else @hhspunter - if you haven't come across it yet,
https://audiokarma.org/forums/index.php?threads/marantz-2220b-speaker-relay-replacement.881545/
There are some peculiarities if you plan to replace the relay. From the picture it looks like yours could be the clear type, which is good!

Yep, mine has the MY2 (marked MY2Z-02, which seems to still be available - although the part numbering explanations I can find are conflicting...).

 

[goldswimmerb]

Fair, but with warm white LED's and two layers of vellum it's pretty dang close.

Woah woah woah - you better not be using CPU grease. That stuff is conductive and not good in this application.

Yes. Matching doesn't matter. MJ21193/4G or MJ21195/6G, whatever is in stock.

Not on the tuner board. Power supply board 3386F, amp board 3386H.

I mean the output emitter resistors or any other big ceramic resistors.

CPU Grease is perfectly fine and in my experience better than the old white stuff they used. You just have to make sure that what you're using is non-conductive, most manufacturers have switched from conductive to nonconductive pastes as the conductive stuff would cause issues for any less-than-optimal computer applications. The main concern would be greases like arctic silver which are very conductive due to the use of metal in the paste.
Arctic MX-4 and MX-5 are both non-conductive and can be had reasonably in large quantities.

 

[hhspunter]

CPU Grease is perfectly fine and in my experience better than the old white stuff they used. You just have to make sure that what you're using is non-conductive, most manufacturers have switched from conductive to nonconductive pastes as the conductive stuff would cause issues for any less-than-optimal computer applications. The main concern would be greases like arctic silver which are very conductive due to the use of metal in the paste.
Arctic MX-4 and MX-5 are both non-conductive and can be had reasonably in large quantities.

I removed the output transistors to allow me to remove the heatsink (making my cleanup easier), and the mica insulators came out unscathed.
I did find these, pre-cut for TO-3 is nice and 6W/mk at 0.3mm thick is not bad for a thermal pad I think? A little pricey for what they are, though. The paste I usually use for my PCs is very high performance and ~12W/mK (Thermal Grizzly Kryonaut). Anyway for 20W through a TO-3 package I am sure anything will be good enough lol.

 

[fromnowon]

I think it's common around here to re-use mica insulators, if they aren't cracked or broken. I would (and have).

 

[hhspunter]

Just gently scrubbed all the boards (well, except for P100 since it's not attached to the rest of them at the moment). Dish soap, soft paint brush, and lots of water. Blew everything out with compressed air until it was mostly dry. Whole assembly is in the oven (preheated to ~170F then switched off before everything went in there - my oven is not very good at temperature control). Currently at about 155F and gradually cooling down. Looking much better now, definitely not perfect but a lot less gross, and will be easier to do detailed cleaning/deoxidizing on anything that needs it.

Once it's dried and cooled down, I will clean and lube all the controls and reassemble it for some testing. They definitely aren't great, here's one of the channels of the volume pot for instance. Applied 1.5V across it and swept it through its range:

 

[hhspunter]

Alright, receiver is mostly back together and powered on without blowing up!

• All PCBs cleaned, dried
• Tone controls removed from PCB and thoroughly cleaned with MG 401B, lubed with Fader Lube
• Volume knob and input selector switch cleaned and lubed
• Balance fader completely disassembled, cleaned, and lubed
• All push-button switches torn down and every springy contact scrubbed thoroughly, switch pin (internal side) also scrubbed. Switches all lubed.
• Evapo-rust used on chassis pieces to get rid of all corrosion - no sanding needed thankfully. Followed up with clear coat to hopefully stave off future corrosion. Low-humidity Colorado helps too Clear coat was scraped from PCB ground pad areas as needed.
• Transformer cover got a quick paint job, managed to save the Marantz label too!
• Due to the extent of disassembly I did, reassembly wasn't a small job - lots of re-soldering wire-wrapping posts (they were removed from PCBs as need to allow disassembly), also had to splice a few wires I needed to cut to disassemble.
• Re-pasted output transistors (reused original mica and repasted)

At this point all components are still original, but hopefully everything that can be serviced without being replaced is in as good of shape as possible (all control pots tested on oscilloscope to verify 100% smooth sweeping). This should give me a good idea for baseline performance before I start replacing components.

To that point, I've found my first mystery - power supply is supposed to be adjusted to 35V via R808 - I am only seeing 41V regardless of where I put R808. R808 is functioning properly (0-4700ohm confirmed). The service manual is sparse on instruction here, I did this with input set to aux, but absolutely nothing plugged in to the unit but power. All switches in the off state.

Also, I tried sweeping through FM stations and the output relay was cycling occasionally - doesn't do it on other inputs, is this normal?

 

[fromnowon]

Hmmm that doesn't seem normal.
Maybe you found it already (and may or may not be contributing to the issues) - there are quite a few errors in Marantz SM's:
https://audiokarma.org/forums/index...vice-manual-error-thread.375907/#post-4869785
^ there are some for the 2220B in that thread.

That's an amazing effort!! It looks great.

 

[hhspunter]

Hmmm that doesn't seem normal.
Maybe you found it already (and may or may not be contributing to the issues) - there are quite a few errors in Marantz SM's:
https://audiokarma.org/forums/index...vice-manual-error-thread.375907/#post-4869785

Yeah I've definitely gone through that thread a few times!
I am starting to narrow down the cause, my H806 emitter should be 14.0V but it reads between 0.5V and 5V seemingly randomly... I've checked most components in that area of the schematic, and other than a bad C808 (should be 3.3uF, was 93pF, replaced it already), everything looks okay. I do need to check the H807 zener diode still.

Edit: Zener diode spec is 14V, extracted it from the board and tested it, measures exactly 14V.

 

[hhspunter]

Okay, power supply is working properly again! H806 did not test out okay on a cheapo multi-function transistor tester (wasn't even recognized). I replaced it temporarily with a C1815, similar specs to the original 2SC945. I do have a 2220B rebuild kit on the way that is supposed to have an H806 replacement, but I think the C1815 should be okay for now at least.

I had tested R806 at some point and it looked like it was spot on at 36k, but by the time I replaced H806, it definitely died - must have been on its last legs. Replaced with a 39k 1/4W and I was able to adjust the output to 35V easily!

 

[hhspunter]

Some initial testing - 10ohm 10W resistors on the output. iPhone 13 Pro with standard lightning-to-3.5mm adapter going into the Aux RCA jacks, input is yellow, pink is right channel and green is left channel. Notice the noise on both channels - guess some parts replacement is in order. I did adjust the idle voltages per the manual (with the corrections from the thread mentioned above).