Issues with one of my blackface bandmaster heads NEED HELP

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Ceylon
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Re: Issues with one of my blackface bandmaster heads NEED HELP

Post by Ceylon » Fri Jul 19, 2019 1:07 am

andy_tchp wrote:
Wed Jul 17, 2019 5:03 pm



Note/warning: These capacitors can contain enough stored energy to cause you serious harm or death, even with the amp turned off.
A bit off topic but just for future reference, can you drain energy from capacitators, making them safe to touch, by unplugging the amp and turning it "on" for a while, thus using up the stored energy?
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Re: Issues with one of my blackface bandmaster heads NEED HELP

Post by Igorilla » Fri Jul 19, 2019 2:34 am

Ceylon wrote:
Fri Jul 19, 2019 1:07 am
andy_tchp wrote:
Wed Jul 17, 2019 5:03 pm



Note/warning: These capacitors can contain enough stored energy to cause you serious harm or death, even with the amp turned off.
A bit off topic but just for future reference, can you drain energy from capacitators, making them safe to touch, by unplugging the amp and turning it "on" for a while, thus using up the stored energy?
I don't think you can do it that way.
But when the amp is on and produces sound, i.e. the power valves are working, you can turn it off (NOT via standby switch!) and unplug. This will in most cases discharge the caps. To be sure measure the voltage across the caps.

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Re: Issues with one of my blackface bandmaster heads NEED HELP

Post by Jaguar018 » Fri Jul 19, 2019 7:19 am

Jazzmastervsjaguar wrote:
Thu Jul 18, 2019 6:33 am
If you do need an amp tech I can not recommend Pete Cage enough. He does great work and his prices a really reasonable. He's out of Damscus MD so not too far from you. Good luck with the amp.

http://www.audiocage.com/services.shtml
I have used him too, and he's great. Not sure if there isn't someone a little closer to Chez Pano, as that's a bit of a trek from the other side of Baltimore to Damascus.

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Re: Issues with one of my blackface bandmaster heads NEED HELP

Post by countertext » Fri Jul 19, 2019 8:29 am

Ceylon wrote:
Fri Jul 19, 2019 1:07 am
andy_tchp wrote:
Wed Jul 17, 2019 5:03 pm
Note/warning: These capacitors can contain enough stored energy to cause you serious harm or death, even with the amp turned off.
A bit off topic but just for future reference, can you drain energy from capacitators, making them safe to touch, by unplugging the amp and turning it "on" for a while, thus using up the stored energy?
I know a few amp builders and techs, and every one of them does most of their amp inspecting and snooping with a wooden chopstick or plastic rod or some such. Like, every time, plugged in or not. I reckon they’re on to something, so I don’t touch anything inside the chassis of my amp.

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Re: Issues with one of my blackface bandmaster heads NEED HELP

Post by somanytoys » Sun Jul 21, 2019 10:35 am

Have you had any luck yet, Pano? or have you not had the time to do much yet?
-David

It's a boost booster, to boost your boost - it makes your tone much muchier.

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Re: Issues with one of my blackface bandmaster heads NEED HELP

Post by panoramic » Mon Jul 22, 2019 8:00 am

somanytoys wrote:
Sun Jul 21, 2019 10:35 am
Have you had any luck yet, Pano? or have you not had the time to do much yet?
I haven't had the time to do anything aside from the tubes check. I am going to take it to big crunch later this week local amp repair dudes/dudettes in baltimore that work out of the magpie cage studio
i used to be cool

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Re: Issues with one of my blackface bandmaster heads NEED HELP

Post by somanytoys » Mon Jul 22, 2019 10:37 am

That's probably a good idea, that way they can check all around under the hood to make sure that there's nothing else iffy lurking around in there besides what's wrong now, waiting to ruin another day.
-David

It's a boost booster, to boost your boost - it makes your tone much muchier.

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Re: Issues with one of my blackface bandmaster heads NEED HELP

Post by panoramic » Mon Jul 22, 2019 11:03 am

yeah if i'm getting it repaired it's going to be gig ready period. I'll keep it upstairs from here on in
i used to be cool

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Re: Issues with one of my blackface bandmaster heads NEED HELP

Post by somanytoys » Tue Jul 23, 2019 10:35 am

Solid plan.
-David

It's a boost booster, to boost your boost - it makes your tone much muchier.

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Re: Issues with one of my blackface bandmaster heads NEED HELP

Post by andy_tchp » Tue Jul 23, 2019 5:02 pm

Igorilla wrote:
Fri Jul 19, 2019 2:34 am
Ceylon wrote:
Fri Jul 19, 2019 1:07 am
A bit off topic but just for future reference, can you drain energy from capacitators, making them safe to touch, by unplugging the amp and turning it "on" for a while, thus using up the stored energy?
I don't think you can do it that way.
But when the amp is on and produces sound, i.e. the power valves are working, you can turn it off (NOT via standby switch!) and unplug. This will in most cases discharge the caps. To be sure measure the voltage across the caps.
I remember reading about that technique, basically turning up loud with a guitar plugged in, strumming some big chords and then turning off the power at the wall, whilst leaving the amp plugged in until the sound had faded out.

I would not rely on this method, and would be using a multimeter to measure the voltages (everywhere) afterwards anyway.

My original suggestion (thinking it's almost certainly the filter caps) was to carefully remove the doghouse and carry out a visual inspection (should Pano feel comfortable doing so), as it will be a decent indication if one is bulging/leaking or has exploded. Either way sounds like a trip to the tech for a once over will have it sorted fairly easily.
"I don't know why we asked him to join the band 'cause the rest of us don't like country music all that much; we just like Graham Lee."
David McComb, 1987.

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Re: Issues with one of my blackface bandmaster heads NEED HELP

Post by panoramic » Sun Jan 12, 2020 6:45 am

https://www.flickr.com/photos/54099386@ ... ed-public/

https://www.flickr.com/photos/54099386@ ... ed-public/

https://www.flickr.com/photos/54099386@ ... ed-public/

https://www.flickr.com/photos/54099386@ ... ed-public/

Last night i went through all of my amps just to spray the pots etc, you know the old annual save myself a trip to the tech evening. Great news, i have my new HRD running in TIP TOP shape, not so great news is what i found inside bandmaster number 2 above (i have 2 of them yes)
here are some pics of it, there is some oxidation inside that is visible, there is also a warp in the board if you look close
I don't know if those have anything to do with what happened to the amp.
I plugged it in last night and tried to play through it, it passes a signal fine just EXTREMELY QUIET which is worrisome, the pots are clean and work fine and the trem still works too, it's just CRAZY quiet and breaks up super easy
i used to be cool

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Re: Issues with one of my blackface bandmaster heads NEED HELP

Post by andy_tchp » Sun Jan 12, 2020 6:57 pm

The boards are all warped by this age, and most chassis will have oxidation visible somewhere.

Wait is this a different amp from the OP?

Either way, I'd still suggest it's likely to be the filter caps in need of replacement.
"I don't know why we asked him to join the band 'cause the rest of us don't like country music all that much; we just like Graham Lee."
David McComb, 1987.

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Re: Issues with one of my blackface bandmaster heads NEED HELP

Post by mbene085 » Sun Jan 12, 2020 7:06 pm

My advice is still to check the tubes first and filter caps second, both of them could be causing this issue.

Still the same caveat that filter caps should only be approached by a tech or someone who knows their amp safety inside and out. It's not worth dying to try to save $100 of work by the tech.

These are the costs of ownership of 60 year old amps.

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Re: Issues with one of my blackface bandmaster heads NEED HELP

Post by Igorilla » Mon Jan 13, 2020 1:59 am

panoramic wrote:
Sun Jan 12, 2020 6:45 am
https://www.flickr.com/photos/54099386@ ... ed-public/

https://www.flickr.com/photos/54099386@ ... ed-public/

https://www.flickr.com/photos/54099386@ ... ed-public/

https://www.flickr.com/photos/54099386@ ... ed-public/

Last night i went through all of my amps just to spray the pots etc, you know the old annual save myself a trip to the tech evening. Great news, i have my new HRD running in TIP TOP shape, not so great news is what i found inside bandmaster number 2 above (i have 2 of them yes)
here are some pics of it, there is some oxidation inside that is visible, there is also a warp in the board if you look close
I don't know if those have anything to do with what happened to the amp.
I plugged it in last night and tried to play through it, it passes a signal fine just EXTREMELY QUIET which is worrisome, the pots are clean and work fine and the trem still works too, it's just CRAZY quiet and breaks up super easy
Some corrosion and warping in the board is normal.

Is your amp quiet on both channels?

You mentioned in the OP that you did try different tubes with no results. As andy-tchp and mbene085 suggested I would suspect the filtering caps too. Swap them out for fresh ones anyway as the amp is'nt been serviced in recent years. But MAKE SURE TO DISCHARGE EVERYTHING of relevance before doing anything. And double check with a multimeter.

You should check the cathode bypass caps, cathode resistors and plate resistors belonging to the preamp and phase inverter tubes next. These are basic amplification units besides the tubes. Your cathode bypass caps look old, so I would simply install fresh ones. The carbon comp resistors drift in value, but sometimes old CC resistors are broken physically which you can check by chopsticking them or by trying to move them.

From the pics, the electrolytic cap in the bias circuit for the power amp looks pretty old. Replace it with a fresh one and check the carbon comp resistor parellel to it as well as the bias pot and the resistor attached to it.

Check for cold and/or broken solder joints.

If you know what you are doing, you can measure the voltages across the circuit and compare to the schematics. This will show you to some extent in which shape the circuit is.

If you don't feel comfortable with doing this yourself and don't know how to discharge the caps before replacing them bring the amp to a tech. It should be an inexpensive and easy fix unless it is transformer related (in which case it is expensive and easy :( ).

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Re: Issues with one of my blackface bandmaster heads NEED HELP

Post by panoramic » Mon Jan 13, 2020 2:22 pm

andy_tchp wrote:
Sun Jan 12, 2020 6:57 pm
The boards are all warped by this age, and most chassis will have oxidation visible somewhere.

Wait is this a different amp from the OP?

Either way, I'd still suggest it's likely to be the filter caps in need of replacement.
nah this is the same amp as the op, this is my 1967
I also have a 1965 which needs service also
i used to be cool

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