Sherwood S7100A Broken Switch by-pass and some pics

[ikonw8]

I was so happy to have bought an excellent condition Sherwood S7100A in October 2016. It needed nothing... even the dreaded power switch worked! All the switches and posts were clean, so I didn't touch anything.

Until...

About two months after I bought it... the power switch failed. Without cleaning.. probably just ageing plastic. The trouble is, my unit failed in the off position.

So, I decided to fix it. It's is an easy repair.

1. Unplug the receiver.
2. Remove the screws on the bottom of the receiver.
3. Slide the wood cover backwards and set it aside.
4. Remove all the knobs. They will all just pull off, no hex keys needed. They may be stiff, pull firmly
5. Remove the nuts on the pots. They are the only things that secure the face plate to the receiver. There should be three. One on both ends and one in the middle.
6. Remove the four screws on the left side, near the front, that secure the tuning / knob frame to the chassis. This will help to give you clearance to remove the volume / power pot.
7. Remove the nut holding the volume pot.
8. Push the volume pot through the hole in the frame, seperate the frame from the chassis slightly to create more room.
9. You need to short the white and brown wire and the rear of the pot.

10. Unsolder the white and brown wire from the rear pins of the pot.
11. Slip on some heat shrink tubing.
12. Solder the end of the brown and white wire together and apply the heat shrink.

13. Now, your receiver will be on, permanently. Test your work, by plugging the receiver back in.
14. Unplug the receiver and add an on/off cord switch to the power lead. I used Atron LA970 (White), but any similar will do.
15. About 45cm from the back of the receiver, part the AC wires. Cut one wire only. Leave the other intact.
16. Attach the cord switch. The intact wire will route through the switch. The cut ends will need to be trimmed slightly. Lay them in the switch. When you assemble the two haves of the cord switch, the cut ends will be pierced to make contact with the wire. Easy.

17. Reassemble the receiver in reverse order of dissambly. You may take the opportunity to clean up the tuning scale glass and remove any dust.
18. Test and enjoy.

Thanks.

 

[jcbuckwalter]

Hey! I've got the same problem as you here, except mine is a S-7100 not a S-7100a. Did you put together the two wires at the very back of of pot/on off switch assembly. I've got a brown wire, same as you, but a red wire not a white one. Are those the ones I should splice together?

 

[ikonw8]

Hi. I will need to open my 7100 up and check the wiring. I have the receiver out, but it might take me until Friday to get to it.

 

[Binkman]

Many have just drilled a hole in the back and mounted an on/off sw.

 

[jcbuckwalter]

Hi. I will need to open my 7100 up and check the wiring. I have the receiver out, but it might take me until Friday to get to it.

Thanks, but I was able to figure it out after some more digging. I was able to put a jumper wire between the brown and red wires. I've got it plugged into a power strip now until I can add a switch on the cord. Thanks for being willing to look!

 

[ikonw8]

Ok. Good to hear you have it fixed!

 

[HiFi in WYO]

Sweet, been waiting for this. Same issue on my 7100A so now I know what to do. It'll be on my list. Love that little receiver. Thanks for posting!

 

[HiFi in WYO]

Never noticed this is a Kenwood.

 

[HiFi in WYO]

Worked perfectly. Thanks!

 

[Waterboi83]

If anyone is still reading this thread maybe they can help me out. Trying to bypass the pot, broken in the off position. Jumped the brown and white wires on the back of the pot, but when I did, resistor r631, a 100ohm (I think) resistor started to glow. I unplugged it before it could completely cook itself. This doesn't seem to match other folks experience bypassing. Thoughts?

 

[ikonw8]

Hi Waterboi. I have this receiver... I think I can try to help you out. Let me get my receiver open, and compare your pictures to mine.

 

[ikonw8]

Ok. In the picture of the volume / power switch, you can see that I have unsoldered the white wire and the brown wire from the switch completely. In your picture, they seem to be still attached.

In the second picture, I show how the white wire and the brown wire are connected together, bypassing the switch.

Of course, you should be able to simply bridge the two together, but I think unsoldering them completely and connecting them together is cleaner.

I hope this helps.

I am not sure why your resistor is overheating. It is possible that the two issues are unrelated or you may need to recheck your work to look for a stray wire or solder bridge.

 

[Waterboi83]

Thanks for taking a look for me. I should clarify what I did: I soldered the white and brown leads like your picture and then plugged in to test, that's when the resistor started glowing/trying to burn itself out. So I unsoldered and resoldered them to the pot and tried just a jumper across them - still glowy/burn. When I don't connect those two wires I don't get the resistor overheating, but my pot/switch is unfortunately stuck in the off position. I was posting to see if anyone had any idea why I was overloading that resistor doing what you and others have done successfully. I should add, that until the pot stopped working the receiver otherwise worked fine.

 

[ikonw8]

Go it. So, you have successfully turned the receiver on! As a result, you get a glowing resistor.

At this point, I would be looking at the power supply and power amplifier circuits for bad capacitors, and check the output transistors for shorts. I wouldn't be turning this receiver on until you troubleshoot the cause.

 

[century tek]

Yeah, that burning resistor has no bearing on the power switch whatsoever. Even if you had a good power switch, that resistor would still smoke. Since the blue wires are coming off of the power transformer secondary, I would be looking at either those diodes or transistors or voltage regulator.

That resistor would not be getting the full line voltage across it because if it was, it would have disintegrated instantly.

It is showing a symptom of something else that is shorted with something that it is also connected to.

Got a schematic by any chance?

 

[DZuberer]

I was so happy to have bought an excellent condition Sherwood S7100A in October 2016. It needed nothing... even the dreaded power switch worked! All the switches and posts were clean, so I didn't touch anything.

Until...

About two months after I bought it... the power switch failed. Without cleaning.. probably just ageing plastic. The trouble is, my unit failed in the off position.

So, I decided to fix it. It's is an easy repair.

1. Unplug the receiver.
2. Remove the screws on the bottom of the receiver.
3. Slide the wood cover backwards and set it aside.
4. Remove all the knobs. They will all just pull off, no hex keys needed. They may be stiff, pull firmly
5. Remove the nuts on the pots. They are the only things that secure the face plate to the receiver. There should be three. One on both ends and one in the middle.
6. Remove the four screws on the left side, near the front, that secure the tuning / knob frame to the chassis. This will help to give you clearance to remove the volume / power pot.
7. Remove the nut holding the volume pot.
8. Push the volume pot through the hole in the frame, seperate the frame from the chassis slightly to create more room.
9. You need to short the white and brown wire and the rear of the pot.

10. Unsolder the white and brown wire from the rear pins of the pot.
11. Slip on some heat shrink tubing.
12. Solder the end of the brown and white wire together and apply the heat shrink.

13. Now, your receiver will be on, permanently. Test your work, by plugging the receiver back in.
14. Unplug the receiver and add an on/off cord switch to the power lead. I used Atron LA970 (White), but any similar will do.
15. About 45cm from the back of the receiver, part the AC wires. Cut one wire only. Leave the other intact.
16. Attach the cord switch. The intact wire will route through the switch. The cut ends will need to be trimmed slightly. Lay them in the switch. When you assemble the two haves of the cord switch, the cut ends will be pierced to make contact with the wire. Easy.

17. Reassemble the receiver in reverse order of dissambly. You may take the opportunity to clean up the tuning scale glass and remove any dust.
18. Test and enjoy.

Thanks.

Another S-7100a back from the switch of death!

A big thanks to y'all for this info on fixing the S-7100a with a dysfunctional on/off switch. I bought this unit in 1973 when I was in grad school at WVU. Used it for a lot of years until the switch just gave out in the off position. When it quit in the early 90's, I dug around to see if a switch could be had. Came up empty back then so the unit (out of its case) was bagged and put under the bed. The case and front panel went into a closet. That was until a few days ago when we were doing some cleaning and I ran across the case in the closet. I went online and searched the S-7100a to see what a broken unit might sell for. That's when I tripped into this thread and that changed everything. I detached the white and brown wires and joined them with a small wire nut. Plugged the unit in and it lit up. Hooked up some small speakers and lo and behold the old unit works. I took the shortcut of adding an inline switch, put everything back together and I'm listening to the unit as I type. So... a big thanks to you folks at Audiokarma for the info allowing me to bring an "old friend" back to life!
Dave Z in College Station, TX

 

[Megaladoink]

Just picked up this beauty from Goodwill bins near my place. Really great condition other then a like crayon mark on then glass(easily came off with elbow grease) and a couple missing knobs. Looked on eGouge and saw a couple for a bit too much so I will wait patiently for them.

But when I tried to turn it on… nothin !!!
I replaced the fuse.. nothing. Realized the volume knob is not the power switch even tho is says power off right where you would turn a knob. Then I just looked at each switch or knob thinking I missed a huge POWER button somewhere. Then found this thread.
So…. now I realized the power cord must have been replaced as it has a switch on the cord. But the baby won’t turn on. I’m guessing something happened to the power switch. Wish me luck. And if there is anybody has 2 treble/bass knobs. I’d love to purchase.

 

[dzkfraser]

I just recently acquired a 7100A - the power switch worked fine but the volume was scratchy. So I opened up and cleaned the pot and now the power switch is stuck in ON - It must be that the plastic thing inside the switch that breaks must have been right on the edge and when I exercised the control after applying the Deoxit - it must have finally broke. Ah well, I could mess aound and rebuild the switch But I have a hard time fixing small things(cause I'm old) and would probably eff it up. And I sure as hell not going to buy that $90 switch on EBay. So I just installed an inline switch on the power cord and all is good. And don't fall into that BS about not installing an inline switch because it will hurt the value of the piece, it's just a power cord for pete's sake. I wouldn't start drilling holes in the thing to install a new power switch though.

 

[ikonw8]

Dzkfraser - totally agree. Just install the inline switch and be done with it. They are beautiful looking receivers, I would avoid cutting them up.

 

[LF240]

The Alps ganged / switched 100k / 100k audio taper pots like those used in the Sherwoods are hard to find (for those of us who refuse to pay 90.00!) however, you can find ganged / switched 10k / 100k Alps pots on ebay pretty cheap. I recently found a seller that sells a pair of the 10 / 100s for 14.95 and ordered them.

I took the switches apart and replaced one of the 10k pots with the 100k from the other switch so as to have dual 100ks. These switches have two shafts (one rotating within the other) so I used an ohm meter to align the pots and drilled a small hole through the shafts and pinned them together.

Kind of a fiddly process, but it worked out quite well.

That said, these switches don't have the loudness taps. If you're a loudness button user you'll have to expend the extra effort of tweaking the tone controls at low volumes.