2270 with bent potentiometers

sssboa

sssboa

Super Member
Hi

I just bought another 2270. It has bent shafts of 4 potentiometers starting from volume, then balance and another 2. The slots in the shafts are pinched too close together as well. The pots are working 100% correctly, no crackling, but the knobs look awkward when turned, not centered. I haven't examined them with the faceplate off yet.
What do you think about trying to unbend them? Is there a high risk of damaging them?
 
Last edited:
That is always tricky to fix.
if you try to bend them back they might break...

in case I don't have the pots/buttons, ...I very often replace only the shaft taking them from other parts.
very often the button are broken, and they soldered to about a million or so cables ==> so I leave them in and just replace the shaft.

same principal could be applied to the pots if don't exact replacement. very often I don't have the right value but mechanically the shaft is the same as another pot I have in my parts inventory.
I used to buy superscope units for super low prices only for the parts which are often the same as in the Marantz units.

luck
Robin
 
tranguru said:
That is always tricky to fix.
if you try to bend them back they might break...

in case I don't have the pots/buttons, ...I very often replace only the shaft taking them from other parts.
very often the button are broken, and they soldered to about a million or so cables ==> so I leave them in and just replace the shaft.

same principal could be applied to the pots if don't exact replacement. very often I don't have the right value but mechanically the shaft is the same as another pot I have in my parts inventory.
I used to buy superscope units for super low prices only for the parts which are often the same as in the Marantz units.

luck
Robin
Click to expand...
I don't know the build of a potentiometer well. I have one badly damaged Marantz volume pot I may take apart and see. I imagine that when I unbend the shafts I may bend the wipers inside the pot as well and will lose a channel etc. You say I can replace the shafts only?
 
Yes - but very tricky I can it component surgery....
if you can wait I will send you the procedure with pictures.
but only on the WE, it is later here in europe and have to travel for the rest of the week
 
I would love to see the pictures for the shaft replacement as I also have a 2230 that has the selector shaft broken. I have a replacement for it but haven't gotten around to replacing it yet. Looks very intimidating with all those wires attached. It would be great if just the shaft can be replaced.
 
tranguru said:
Yes - but very tricky I can it component surgery....
if you can wait I will send you the procedure with pictures.
but only on the WE, it is later here in europe and have to travel for the rest of the week
Click to expand...
OK, I am waiting. And you'd better find a nice motel before the cold night catches you on the road :)
 
For the tone controls, I would seriously consider getting a parted out tone control board with the pots mounted off of the auction site. There are a couple of those boards up for sale right now. The likelihood of getting four bent shafts to ever look right is slim to none. Replace the board and three of the four are fixed. I probably would also look for a volume control pot too. Yes, some people have been able to use some heat and get a reasonable fix without breaking anything. But with this many bent ones, I would replace. Just my $.02.

P.S. Before buying a board, question the seller to guarantee that the shafts are perfectly straight with no wobble when turned.
 
Steven Tate said:
For the tone controls, I would seriously consider getting a parted out tone control board with the pots mounted off of the auction site. There are a couple of those boards up for sale right now. The likelihood of getting four bent shafts to ever look right is slim to none. Replace the board and three of the four are fixed. I probably would also look for a volume control pot too. Yes, some people have been able to use some heat and get a reasonable fix without breaking anything. But with this many bent ones, I would replace. Just my $.02.

P.S. Before buying a board, question the seller to guarantee that the shafts are perfectly straight with no wobble when turned.
Click to expand...
Will it be for Bass, Mids and Treble?
 
So to recapitulate.
What is the risk?
Only that the shaft can break?
I was concerned that by unbending/bending the shaft I can affect arrangement of the insides (wipers etc.) and e.g. lose one channel. Is it real or the build of the pot prevents it from happening?
 
sssboa said:
What's the brass nut around balance shaft?
Click to expand...
This is present on quite few models, and is there just to hold the faceplate in place as you found out :D

It is supposed to unscrew....and then the faceplate is free to come off. Is yours stuck ? it looks a bit abused :eek:
 
Just a threaded brass keeper. You should be able to use the tips of needle nose pliers to gently unscrew it. Looks as though somebody hasn't been so gentle in the past according to the marks on the faceplate.

Edit: I replied before updating the page so I didn't see the reply above. Sorry.
 
Dearslayer said:
Just a threaded brass keeper. You should be able to use the tips of needle nose pliers to gently unscrew it. Looks as though somebody hasn't been so gentle in the past according to the marks on the faceplate.

Edit: I replied before updating the page so I didn't see the reply above. Sorry.
Click to expand...
Yeah, done.
 
Two problems I see with the straightening procedure: 1) the shaft is very brittle and prone to break. Some people heat it with a hair dryer or some other type of heater and slowly bend it into position. Which leads me to 2) the odds of getting one shaft perfectly straight where the knob tracks straight as you turn it is very slim. The odds of getting four of them like that? Zero. Of course, there is no problem with trying to straighten them. Worst thing that happens, they break. But with four of them, I would still be looking for exact replacements and just replace them.
 
Always use tape or Saran wrap or something to keep tools from marring the face plate.
I never tighten the face plate nuts, screws or bolts more than just past finger tight.

YMMV
Tom
 
If the shafts are only bent a little, you should be able to straighten.

I have never had a badly bent shaft, but certainly they exist. Most of the time it is bent at the bottom of the split-shaft slot just behind the knob, with the two halves bent not the solid part of the shaft. This can be straightened if not too bad, but if it is bent very much at that notch you will risk it breaking at the bottom of the notch where it is bent.

Use a small screwdriver and a knife blade, slowly force a knife blade between the halves while pushing toward the bent-in half. Once you have it apart enough to insert a small screwdriver from the end of the slot inward (down the shaft) (should be a screwdriver no thicker than the normal spacing of that slot), slowly drive the screwdriver down like a wedge, pulling toward the bent-in half of the shaft. Once it is completely inserted, you can pull the end of the screwdriver over to straighten the bent-in half, very carefully. It wouldn't hurt to have a vice-grip clamped at the base of the slot at this point to keep the forces inward at that point.

The sharp corner at the bottom of the slot is your enemy, it is a tremendous stress-concentrator and is where you will break the shaft if it happens. Heat? Unless you're getting the shaft close to its melting point, I can't see where this will make any difference. If anything has a chance of helping it would be to use a Dremmel or similar to round the bottom of the slot and eliminate the sharp angle at the bottom of the slot, which would distribute the stresses and involve more of the shaft in the re-bending process.

Getting this straight within 1mm? It only has to look good, if it does you've succeeded. This isn't a turbine shaft.

Good luck.
 
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