2250B broken Balance sliding potentiometer and audio issues.

[r_s_guy]

The balance slider pot on my 2250b is broken within. Any body know of a replacement? Can it be super glued? Or is the internal components can't be joined once severed like that?

Found this while trouble shooting an issue with extremely low volume only on right channel and almost zero on left. Power amp is good. Preamp components have mostly been replaced (caps and transistor) and issue is the same, until I found the severed balance pot. Could this be the cause?

 

[wlhd1610]

Yes ,that would cause a dead preamp output.
Some may suggest trying to epoxy it back together and putting some kind of carbon tracking material on the carbon sliding path but that's not gonna happen.
You need a replacement donor balance slider.
They are available if you look.


Bob

 

[Oerets]

Welcome to AK!


That one looks to far gone. It can be repaired, just the slider is snapped so why?

Look for a replacement in good condition.

 

[r_s_guy]

It doesn't seem easy to find the exact donor part. What spec would I need to search for, for if a new replacement? I knows it is 500K Ohms. Can this value be different? Dual potentiometer? Linear? Anyone have a link?

Meanwhile, Is there a way I can bypass the balance pot so I can test the unit and the rest of the preamp board? Schematics show the signal coming from the preamp through the volume pot, into the balance pot and on to JT22 and JT21 on the Monitor/Dolby board.

Thanks

 

[wlhd1610]

I believe the 2220B and a few others have the 500K balance slider.
I'll check to see what others have it.

Bob

 

[cjenrick]

are you going to sell the receiver? if not, you could hard wire in some fixed resistors to simulate the balance control electronically and mount the broken part on there with the knob for looks,

those sliders are tough to find, we have a 2250 that has been waiting for a balance control for about a year now. this one is extra tough to find because it has taps for the loudness function. if that knob gets smacked hard enough the fragile phenolic type material snaps like a dry twig in a stiff desert wind,

search evilbay by "Marantz 2250B parting out" and see what gives. there are a few Marantz restore geeks that have websites with some parts for sale but it can be slim pickins and expensive so i feel your pain

 

[jFF_Bulbo]

Bypass the balance por is not an option?

 

[wlhd1610]

View attachment 1604383 View attachment 1604384

The balance slider pot on my 2250b is broken within. Any body know of a replacement? Can it be super glued? Or is the internal components can't be joined once severed like that?

Found this while trouble shooting an issue with extremely low volume only on right channel and almost zero on left. Power amp is good. Preamp components have mostly been replaced (caps and transistor) and issue is the same, until I found the severed balance pot. Could this be the cause?

Does it look like this one?



Bob

 

[r_s_guy]

Hi Bob,

Yes! That's exactly the part number. Are you selling it?

Thanks

Ruben

 

[r_s_guy]

Meanwhile I ordered a NOS part that had the exact dimension, but it is a 100K Ohms pot. What will that do to my balance function?

Also, I bypassed the pot and hardwires the wires, I got good sound out of left, but still same low volume out of right. Could that be because of not usinb a pot? Or some other issues along the signal path?

 

[wlhd1610]

You really should use the correct 500k ohm one.
100k will not have the correct taper/resistance for the 2250B.

I had sent you a PM yesterday.

Bob

 

[r_s_guy]

Hi, here is an update. When I had jumped the wires to bypass the broken balance slider, I had gotten good sound from right channel, and no sound from the left.

Thanks to Bob (wlhd1610) who supplied the replacement slider, I slipped it into circuit. I however, I continued to get good sound on the right, and balance slider worked only on the right. Left was still silent. Also, tone mode on off was giving a loud ground hum.

Upon inspection, I saw a crack in one of the wafer circuit board of the tone mode switch assembly. This had put a gap on 3 of the circuit traces. Bob again offered to send me the correct part, but I managed to fix it myself.

I disassembled the parts holding the wafers, by unscrewing the nuts and sliding the shafts back. (carefully, there are tiny parts). I then unsoldered the legs and took the cracked board out. First I superglued the crack. Then I scratched off a small part of the protective layer to expose the copper trace on either side of the crack. Then applied Flux to it and tinned it with solder. I then soldered a lead wire across the gap for each trace. Then reassembled it and soldered the legs back on. Pictures attached.

Then turned the unit on, and viola! I had sound on both left and right channel
Good sound, no hum, no crackles. The balance slider worked perfectly too.

My issue is resolved! Thanks to Bob for your help! Now to continue on with soldering the balance slider in and recapping the rest of the unit, and I'm done!

 

[r_s_guy]

Missed picture of the new balance sliding pot clipped on to circuit to test.

 

[r_s_guy]

I had asked in the forum if the the balance sliding potentiometer could be bypassed. And I found out it could, as shown in the picture. I got good output wired this way, just couldn't taper off on L or R, that's all.

 

[tonebells]

Tony

 

[wlhd1610]

Nice job on the wafer switch repair!

Bob

 

[r_s_guy]

So, I now have a non functioning balance slider potentiometer that I am willing to give away to anyone that wants to salvage whatever is remaining of it, since it's somewhat of a rarity - housing, plastic connector, teeny ball and spring (which is SO easy to lose). Just DM me and pay postage.