Yet another Heath W5M rebuild
- Thread starter ab0ez
- Start date
ab0ez
AB0EZ
Huh, I don't think I have seen that before. That's pretty strange!
billinchile
Member
This thread (and the previous one of the WM5 rebuild) are great resources for those of us attempting to keep these amps performing as they should.
I live in Brazil, and have a single WM5 that I got off the Bay several years ago (2 months shipping time - must have come by boat - and even so the freight cost was half the selling price). It was in so-so condition (with some rust inside the chassis) and it had all the original components from the kit.
I recapped it and replaced all of the composition resistors, retaining the two precision 30-ohm ones. I purchased NOS Sylvania 12AU7s and Chinese KT66 tubes. The rectifier is a RCA branded 5R4GY. I replaced the tube sockets with ceramic ones.
After my rebuild, the amp had high hum. It went into a closet and stayed there for a while. Reading the re-build thread inspired me and now I have it on my bench.
I've gone over the entire amp, checking all of the wiring against the manual. I suspect that the hum has something to do with grounding. I noticed that the phono plug jack wasn't isolated from the chassis, so I did that. But the hum persists, and what is particularly disturbing is that I measure continuity between the ground buss and the chassis. Where might I look on the amp to discover the reason for this? Thanks for any advice you can provide.
I live in Brazil, and have a single WM5 that I got off the Bay several years ago (2 months shipping time - must have come by boat - and even so the freight cost was half the selling price). It was in so-so condition (with some rust inside the chassis) and it had all the original components from the kit.
I recapped it and replaced all of the composition resistors, retaining the two precision 30-ohm ones. I purchased NOS Sylvania 12AU7s and Chinese KT66 tubes. The rectifier is a RCA branded 5R4GY. I replaced the tube sockets with ceramic ones.
After my rebuild, the amp had high hum. It went into a closet and stayed there for a while. Reading the re-build thread inspired me and now I have it on my bench.
I've gone over the entire amp, checking all of the wiring against the manual. I suspect that the hum has something to do with grounding. I noticed that the phono plug jack wasn't isolated from the chassis, so I did that. But the hum persists, and what is particularly disturbing is that I measure continuity between the ground buss and the chassis. Where might I look on the amp to discover the reason for this? Thanks for any advice you can provide.
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Can you post a clear picture(s) of the insides of the amp? Might help someone to give you ideas.
John
A couple of things come to mind...
Check all of your solder joints.
Make sure all of the appropriate wires are twisted and routed properly.
One of my W5m's had a slight hum when I finished it, turns out that I had a couple of less than desirable solder joints.
You might want to pull the signal tubes (one at a time), and see if the hum stops. If that's the case, you've potentially identified the part of the circuit that is causing the hum.
Check all of your solder joints.
Make sure all of the appropriate wires are twisted and routed properly.
One of my W5m's had a slight hum when I finished it, turns out that I had a couple of less than desirable solder joints.
You might want to pull the signal tubes (one at a time), and see if the hum stops. If that's the case, you've potentially identified the part of the circuit that is causing the hum.
billinchile
Member
Thanks for your reply. I discovered that the original builder had connected a wire from the Spirashield (that covers the two black wires coming from the OT and that go to socket AA) to the ground bus. I removed the wire.
However, I have a much more serious problem. Now when I measure the tube pin-out voltages I get readings of only a few volts. Same thing for the voltage readings at the two multi-section electrolytic cans. A few days ago, they all tested a bit higher than given in the specs of the manual. All of the tubes test good. All of them glow happily, except for the rectifier (but I'm not sure if I should see any glow there). When I run AC into the amp from a variac, the the tubes glow beginning at around 40VAC and are bright by 117VAC. With pin voltage readings of only a few volts, should the tubes light up at all? I'm stumped. How should I proceed? Any advice will be very welcome (except for taking it to a tech; there are none that I know of in my city of 3 million. In Brazil, the most common comment when people see tube equipment is "hey, my grandfather had a radio that used those").
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billinchile
Member
I hope that somebody will respond and answer my questions.
ab0ez
AB0EZ
Hi Guys,
I'm going to make an attempt to get back on AK. I've been crazy busy with my job and away from home about 3 weeks out of each month for longer than reasonable.
Give me a chance to rejoin AK this weekend and I'll post some more pictures, etc on this and another thread/project or three.
I sure hope the level of snarky-ness has diminished since I last posted!
Jim, AB0EZ
I'm going to make an attempt to get back on AK. I've been crazy busy with my job and away from home about 3 weeks out of each month for longer than reasonable.
Give me a chance to rejoin AK this weekend and I'll post some more pictures, etc on this and another thread/project or three.
I sure hope the level of snarky-ness has diminished since I last posted!
Jim, AB0EZ
Welcome back - look forward to the updates!
ab0ez
AB0EZ
Well I tried to post a recent pic of one of the W5Ms, but I am out of space to upload any pics until I rejoin AK.
My wife and I both use Ebay. I have the password to log into ebay and she has the paypal password. Works great for us since we both have to concurr on all purchases! That's why I will wait until this weekend to join back up.
If anybody wants the pic posted I can email it to them and they can post it here on my behalf.
My wife and I both use Ebay. I have the password to log into ebay and she has the paypal password. Works great for us since we both have to concurr on all purchases! That's why I will wait until this weekend to join back up.
If anybody wants the pic posted I can email it to them and they can post it here on my behalf.
s-petersen
Scott
I've seen that,but I think it comes from stacking the amps on other equipment,or mishandling them in some way
Hi, Jim
Happy to see your back, the good thread that you build is sure helpful. After looking through the thread, I decided try to rebuild my pair of w5m. Does it possible to have the final schematic of your rebuild and parts list email to me for helping my rebuild. It is because I can not sure some parts details when seeing the photo attached to your thread.
Happy to see your back, the good thread that you build is sure helpful. After looking through the thread, I decided try to rebuild my pair of w5m. Does it possible to have the final schematic of your rebuild and parts list email to me for helping my rebuild. It is because I can not sure some parts details when seeing the photo attached to your thread.
That needs an Admin; you should PM Grumpy or luvvinvinyl with the details and they will resolve your status.
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