Please Help Me Trouble Shoot 64 Bandmaster

[JoeM]

DAB, aren't you located somewhere in SoCal?

[soundguruman]

Arrrrrrrg…WTF Bob! You have had at least two offers from members of this board to do hands on work to fix your amp. Now you want to send it off to another remote shop that will gut the whole board and start over? Now you want “clean with some balls” My dog can clean his balls but it doesn’t help my tone.

You don’t know what’s wrong with your amp and you don’t have the background to fix it. That is not your fault. You did good to ask questions here but then you didn’t take the advice offered. I feel safe to say that I’m not the only member frustrated by that. When someone asks you to do a specific test or answer a specific question it is to help them troubleshoot your amp. That’s part of the process of isolating the problem. What’s expected and what would be helpful is a clear and concise answer to the question. The story of how you have let yourself be mistreated has been sufficiently documented. We don’t need to hear any further rants about that. If you were to print out all the postings in the five different threads you started about this problem and read them in chronological order you will understand what I’m getting at. You can skip the recent posts in the “Pulled Coupling Caps” thread where people have gone on to discuss other topics. That was an interesting morph by-the-way. It’s very similar to what happens at a party when the original leader of a conversation looses the interest of the other participants and everyone drifts away to discuss topics that they find more interesting and productive.

So Bob…DON’T BE A DUMBASS. You picked the name but it’s not required that you live up to it. If you want the original mojo back in your Bandmaster then review the threads and take advantage of all the advice from the experienced and knowledgeable people who have been trying to help you. That advice has been free to you but it did cost the contributors time that they could have spent on their own projects.

The End (of Tom’s rant … for now … maybe)

1010

Bet you $1 it's blown speakers, and there has been nothing wrong w/ the amp.

[dumbassbob]

DAB, aren't you located somewhere in SoCal?

I live in Dana Point thats South Orange county

[Leo_Gnardo]

At some point it must occur to us that a new eyelet board stuffed with new parts could be wired in place of the old, and probably eliminate the issues in the process for a hell of a lot less money than has been and will be spent.

Would have to be a 'special' with the murkytone filter points added. Also considering black tag board is a crap shoot these days could bring in a host of new problems. Leaky black boards - even new - I'd do it on turret board just to stay away from the SOS problems I gotta solve every day on old Fender amps that are - nearly - working. Dream on, not much chance of that happening. But, ya never know...

52 Bill, still wondering where you got that schemo? Inquring minds want to know, both of mine, maybe others...

DAB, measurements I asked for? Don't give up quite yet.

[Leo_Gnardo]

I live in Dana Point thats South Orange county

Crikeys !!! Been there, some goofy hotel with "theme" rooms, it's weird. Done shows at the Coach House. Dana Point, a nice place to raise your kids up.

[dumbassbob]

Ah but does it help HIS tone? I'll bet he thinks it does. I could propose an experiment here but this is a family show so I won't.

------------------------------------------

OK back to the deflicted Bangmaster.

Never did get a measurement of input R. Bob, you can just plug a guitar cable in, & measure the R from sleeve to tip. You said those 1M measured low, this will tell us how low.

Bad bright switches? easy enough to measure whether they switch or not. Another ohm meter task.

What with all the in & out of those domino caps I wonder if they're still working at all. If they're open, that would sure as heck stop all treble. You could tack solder another cap say @ 0.001 uF around them (in parallel) and if treble picks up then you know where's the treble trouble.

Exploding bias filters. Harrumph! Won't be having that. I wonder if his majesty the royal Bloviator of Texas or his assistant put in caps with too low a voltage rating. Fender often did and got away with 25V caps in circuits that delivered over 60V but not for long. Gelard Weber could have made the same misteak that Saint Cesar did, and think they could get away with it because Leo Fender did. Not recommended. Make sure the bias cap is rated 75V - 100V and installed in the correct direction. Also a weak or underrated rectifier could wreck a cap. I use UF4007, if you don't have any ready to hand the more common 1N4007 works fine. Rated 1000V PIV - defnitely won't go bad in the bias circuit. If the bias department has been holding together recently, not much reason to worry, but DO check the voltage rating on the bias cap.

Say I just had another tiny brain wave. IF the bias pot/resistor lost its ground connection, that could cause the voltage on the bias supply to rise, and pop the cap. Also would clamp down the bias current in the output tubes and make everything sound like crap. Small, and awful. For a lark, let's measure the bias voltage, OK DAB?

That cap with the lifted leg, ask Tom's dog what that means but seriously it don't mean a thing if it's not connected. Except sloppy work. HOWEVER here's another potential trouble spot. If that cap - the one that's connected - is leaky or shorted, that would also explain lousy sound. Measure here too, Bob, voltage on each end of that 500 pF cap. Could be a clue. Would affect both channels at once.

Pots? Yes if they were changed but that doesn't explain why the sound deteriorated. You could measure 'em, make sure nothing's gone goofy there. They look original in the photos but - who knows.

You could send it here too. Won't be free, but it will be fair. And I'll report the results so we can all get some relief. Like Tom's dog... Puh-leeeze don't send it off to GW or any unknown entity. I know there's a lot of folks who are beyond the point of caring, but there's also some who would like to see this problem sorted out and know why it's been so goofy. This case helps take my mind off of even more annoying things - in the news - I'll leave that to yer imaginations.

I will get on this after work Saturday,Do I need to have the tubes in and the Amp On?.I cut the one 500pf off.I don't know why GW did that,What about the sockets? some are pretty loose...they move...Thanks again DAB

[Tom Phillips]

Bet you $1 it's blown speakers, and there has been nothing wrong w/ the amp.

Back in the history of the discussions about this amp DAB did confirm that he tried different speakers AND different speaker cables and it did not improve the sound.

[52 Bill]

The schematic was Photoshopped from the AA763 original. That's why there is no value for the added cap, I could not see the color dots in the two photos.

[Jazz P Bass]

I wonder if the main filter caps where changed in all of this.
(I don't have the time nor the inclination to reread this post)
Now THAT right there would totally blow what the amp was.
They could have been a tad funky & the sound achieved was pleasing to the OP.
Install new caps & 'Hey, what did you do to my amp?'

[g1]

I wonder if the main filter caps where changed in all of this.
(I don't have the time nor the inclination to reread this post)

Post #33, and post #58 edit2 where Leo was speculating a similar theory.
http://music-electronics-forum.com/t34032/#post315065
http://music-electronics-forum.com/t34032-2/#post315184 (edit2)

[Leo_Gnardo]

The schematic was Photoshopped from the AA763 original. That's why there is no value for the added cap, I could not see the color dots in the two photos.

Thanks Bill! Good photoshopping - sure had me fooled. Attention photoshoppers, blue light special on murkytone circuits!

g-one, Jazz P Bass, 52 Bill, & all...

DAB's going to make some measurements when he gets home from work. Maybe we'll get some clues, maybe not. He said one of those 220K's was cracked & presumably open circuit (since replaced), and amp still sounded duff. We'll get him to try a couple more simple fixes that can be done at-home. If no joy, then it's time to send it to someone who's familiar with his problem and will get it right. Which one of us will be the lucky one - to dance with the monster tonight?

[dumbassbob]

I cut the 2nd 500pf cap out,I don't know why GW did that,and the leg was Not Soldered..With a 1/4 in plug in the inputjack measured 1.053M...... The switch measured 1.528k..

[Leo_Gnardo]

I cut the 2nd 500pf cap out,I don't know why GW did that,and the leg was Not Soldered..With a 1/4 in plug in the inputjack measured 1.053M......

OK, so far so good...

The switch measured 1.528k..

Across a bright switch? If the switch is up should be zero or nearly. Down it should measure open, or infinite ohms. Give 'em a little shot 'o cleaner spray, click 'em up & down a few times, & re measure ohms from one switch terminal to the other please. And the other bright switch too.

Granted, bright switches probably aren't the problem but might lead to a clue.

[dumbassbob]

Ah but does it help HIS tone? I'll bet he thinks it does. I could propose an experiment here but this is a family show so I won't.

------------------------------------------

OK back to the deflicted Bangmaster.

Never did get a measurement of input R. Bob, you can just plug a guitar cable in, & measure the R from sleeve to tip. You said those 1M measured low, this will tell us how low.

Bad bright switches? easy enough to measure whether they switch or not. Another ohm meter task.

What with all the in & out of those domino caps I wonder if they're still working at all. If they're open, that would sure as heck stop all treble. You could tack solder another cap say @ 0.001 uF around them (in parallel) and if treble picks up then you know where's the treble trouble.

Exploding bias filters. Harrumph! Won't be having that. I wonder if his majesty the royal Bloviator of Texas or his assistant put in caps with too low a voltage rating. Fender often did and got away with 25V caps in circuits that delivered over 60V but not for long. Gelard Weber could have made the same misteak that Saint Cesar did, and think they could get away with it because Leo Fender did. Not recommended. Make sure the bias cap is rated 75V - 100V and installed in the correct direction. Also a weak or underrated rectifier could wreck a cap. I use UF4007, if you don't have any ready to hand the more common 1N4007 works fine. Rated 1000V PIV - defnitely won't go bad in the bias circuit. If the bias department has been holding together recently, not much reason to worry, but DO check the voltage rating on the bias cap.

Say I just had another tiny brain wave. IF the bias pot/resistor lost its ground connection, that could cause the voltage on the bias supply to rise, and pop the cap. Also would clamp down the bias current in the output tubes and make everything sound like crap. Small, and awful. For a lark, let's measure the bias voltage, OK DAB?

That cap with the lifted leg, ask Tom's dog what that means but seriously it don't mean a thing if it's not connected. Except sloppy work. HOWEVER here's another potential trouble spot. If that cap - the one that's connected - is leaky or shorted, that would also explain lousy sound. Measure here too, Bob, voltage on each end of that 500 pF cap. Could be a clue. Would affect both channels at once.

Pots? Yes if they were changed but that doesn't explain why the sound deteriorated. You could measure 'em, make sure nothing's gone goofy there. They look original in the photos but - who knows.

You could send it here too. Won't be free, but it will be fair. And I'll report the results so we can all get some relief. Like Tom's dog... Puh-leeeze don't send it off to GW or any unknown entity. I know there's a lot of folks who are beyond the point of caring, but there's also some who would like to see this problem sorted out and know why it's been so goofy. This case helps take my mind off of even more annoying things - in the news - I'll leave that to yer imaginations.

1) the bias cap is a 100-100 now,2)I cut the one 500 out and the one that is there now is 510..The original cap reads 515,wonder why he did this...The filter caps were changed the first time I sent it,You don't think something might be wrong there..How do I measure the filter caps?I do not have a dummy load,but could I use a 60 watt speaker put all the tubes back in, power it up,put one hand in my pocket?Also if I put the red probe where the 2- 220R come to a point, Is that where you read Bias? I wonder if GW set it cold..I still have not done the chopstick test,.I am still looking to see if any Resistors bad...Thanks to you and Tom,soundguru and Bruce for taking the time to help me...

[Leo_Gnardo]

1) the bias cap is a 100-100 now,2)I cut the one 500 out and the one that is there now is 510..The original cap reads 515,wonder why he did this...The filter caps were changed the first time I sent it,You don't think something might be wrong there..How do I measure the filter caps?I do not have a dummy load,but could I use a 60 watt speaker put all the tubes back in, power it up,put one hand in my pocket?Also if I put the red probe where the 2- 220R come to a point, Is that where you read Bias? I wonder if GW set it cold..I still have not done the chopstick test,.I am still looking to see if any Resistors bad...Thanks to you and Tom,soundguru and Bruce for taking the time to help me...

Bias cap OK, the 500 pF, big so what if it's off by a couple percent. Hi Voltage filter caps are likely OK but it MAY have been the transition from old barely working filters to new ones that's been foxing us.

Still suspecting those domino caps. If they went open circuit due to overhandling, tweaking the leads back & forth while removing, replacing, removing, replacing, that would give you a no-treble amp for sure. You could parallel or substitute with a 0.001 uF or any nearby value you have on hand.

I measure the bias V at the ends of those 220K's where they meet the caps, but it should be nearly the same at the point where they join. Also, I'd like to see a voltage measurement on each side of that 500 pF cap. Yes hand in a pocket or behind your back will keep a shock from stoppin' your heart, the last thing we need at at this stage, or any time for that matter. Ya gotta survive to enjoy your working amp, eventually, hope it's soon.

Would also be good to resistance check the volume treble & bass pots but let's find out what happens with these other tests first.