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Post subject: Re: Help Bandmaster blowing fuses
Posted: Sun Jul 22, 2012 6:11 pm
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Toppscore wrote:
Check your home's electrical power output.
Simple as that :lol:

Toppscore 8)


Sorry but it's not really as simple as that.

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Post subject: Re: Help Bandmaster blowing fuses
Posted: Sun Jul 22, 2012 6:16 pm
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Arc-n-spark wrote:
Toppscore wrote:
Check your home's electrical power output.
Simple as that :lol:

Toppscore 8)


Sorry but it's not really as simple as that.


Forget it, Ken.

He hasn't quite figured out that this is where the big boys play and he's as clueless as an extra from "Deliverance" at a Mensa Convention.

:mrgreen:

Arjay

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Post subject: Re: Help Bandmaster blowing fuses
Posted: Sun Jul 22, 2012 6:32 pm
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Thanks Toppscore, really wishit would be that easy as dirty power but it is the same in different rooms guess I need to check my power. Almost ready re-cap this sucker because it seems that I'm getting pretty much the correct power at the points except the two points on the 12ax7's. Again thank you all for the help. It is appreciated and you have given me a lot of inspiration. You know the problem is right in front of me and I'm gonna find it. Guess it's self satisfaction...lol :P


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Post subject: Re: Help Bandmaster blowing fuses
Posted: Sun Jul 22, 2012 6:40 pm
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Thanks for the info, Musicman!! So just to get a better focus, this amp has the 763 bias control, right? If you pull all the tubes, with exception of the 5U4GB, can you check all the PT voltages? Then the filter caps and bias supply voltages. The amp would have to be switched on and in the play mode for this test. Also it would be benefical to know if the fuse is OK, with only the rectifier tube in the amp. Don't mean to ask too many questions! Art

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Last edited by aclempoppi on Sun Jul 22, 2012 7:04 pm, edited 1 time in total.

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Post subject: Re: Help Bandmaster blowing fuses
Posted: Sun Jul 22, 2012 6:51 pm
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MusicMan, I'd take voltages before and after that 100k-ohm, 1-watt drop down resistor from C-point 360VDC and the anode of the second half of the 12AX7 (7025)-- 230VDC. AND look at that 0.1mfd coupling cap BEFORE the 220k-ohm resistor. It maybe leaky.

Here's my quick-&-dirty method to test for leaky coupling caps:

For coupling caps, I disconnect the lead of the cap going to the next grid stage. You'll notice that one end is usually hooked to the last stage's anode plate and the other to the next stage's signal grid.

Be careful here: you are going to measure voltages with the amp on. Amp on, not in Standby mode, no inputs, volume(s) at zero, speaker(s) connected.

Hook the red wire of your DVM to the lifted cap lead. The black wire to the chassis ground. Set meter to read Voltage-DC.

With amp on you should only "see" a few mV. If you are reading close to or above 1VDC... you can consider the cap "leaky."

If you read on the other lead of the cap (the one that is still soldered to the circuit). You prolly "see" a few hundred VDC. Maybe, somewhere between 100-300 VDC. Best to check schematic, to find what VDC should be read, at which points of the circuit.

This is why it's best to choose good quality, high VDC rated caps (400-600VDC). They have less chance of breakdown and going bad or leaky. You can see the consequences of a leaky cap.

Least consequence is resetting the idle bias level of next stage way outta linear region. Worst consequence is a fried tube, when a few hundred VDC is past onto a grid designed for only mV of DC.

Good luck! HTH.


http://www.webphix.com/schematic%20heav ... _schem.pdf


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Post subject: Re: Help Bandmaster blowing fuses
Posted: Sun Jul 22, 2012 7:19 pm
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Good deal, Beemer. IMO those voltages measured at V5's 220K are fine. Art

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Post subject: Re: Help Bandmaster blowing fuses
Posted: Sun Jul 22, 2012 7:35 pm
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Thanks Professional Musician. I took all of the tubes out except the rect. tube and yes it looks like all of my high volt. are there, most are 525 V. The fuse is fine, and I rewired the bias circuit to match the 763 circuit but as of yet haven't changed the resistor to the 470 1W and the cap to a 25/50. I will check the coupling caps. Thanks Art and BMW2002Ti .. :)


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Post subject: Re: Help Bandmaster blowing fuses
Posted: Sun Jul 22, 2012 8:12 pm
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Seems like you're making headway, Musicman! I'd go with a 470ohm 1watt metal oxide and a 50uf 100vdc cap, for that bias supply. I'd also consider those same resistors for the output tube screens. Those resistors could be 1 or 2watt. JMHO Art

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Post subject: Re: Help Bandmaster blowing fuses
Posted: Thu Jul 26, 2012 2:01 am
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Retroverbial wrote:
He hasn't quite figured out that this is where the big boys play and he's as clueless as an extra from "Deliverance" at a Mensa Convention. Arjay


"Big" is a good description of you trying to look down past your chin & belly :lol:
"Boy" ~ is what you feel but cannot see ~ just look down :lol: :lol:
"Play" ~ look down and see yourself play at work :shock:
Deliverance ~ is being "ridden sooooweee" ~ your one scene acting career :lol: :lol: :lol:
Mensa ~ at least you know how to spell your home address :lol: :lol: :lol: :lol:


Need Mensa Clinic training? Having trouble knowing which end is "important" :?: :?: :?:
Image

Ahhhh forget it gang. He hasn't quite figured out which end to speak from.
Give BIG BOY time to PLAY so he can DELIVER HIMSELF from HIMSELF :lol: :lol: :lol:
:roll: :roll: :roll: :roll: :roll: :roll: :roll: :mrgreen: :mrgreen: :mrgreen: :mrgreen: :mrgreen:

Toppscore 8)

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Post subject: Re: Help Bandmaster blowing fuses
Posted: Thu Jul 26, 2012 3:27 am
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Topp, no offense, but we're trying to focus on the fuse (over current) blowing problem. Checking an amp on the internet isn't easy. But we try to be as helpful and specific as possible. Please offer no distractions to our effort. Thanks, Art

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Post subject: Re: Help Bandmaster blowing fuses
Posted: Thu Jul 26, 2012 3:35 am
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aclempoppi wrote:
Topp, no offense, but we're trying to focus on the fuse (over current) blowing problem. Checking an amp on the internet isn't easy. But we try to be as helpful and specific as possible. Please offer no distractions to our effort. Thanks, Art


Art, very well understood. Idiot needs to cut the crap.
It's been great around here, lately (Rain Man excluded).

My comment about the home voltages amps watts ohms, etc.
inconsistencies was quite serious, as I've experienced in my home.
Glad the issue is elsewhere as home electrical improvement/repair
costs more than several amps. Toppscore :)

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Post subject: Re: Help Bandmaster blowing fuses
Posted: Thu Jul 26, 2012 4:15 am
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Topp, JOC... what AC line conditions caused the fuse to blow out in the amp? The only time I've ever seen fuse-blow issues is with low voltage (brown-outs). And sudden use of a current hog (like an air condtioner or refrigerator) usually causing the main's circuit breaker to trip --- not the unit's fuse (or breaker).

Excess VAC just causes the amp to run at higher idle wattage values. But, the amp prolly is drawing less current, under these conditions.

Thanks!


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Post subject: Re: Help Bandmaster blowing fuses
Posted: Thu Jul 26, 2012 4:51 am
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BMW2002Ti wrote:
Topp, JOC... what AC line conditions caused the fuse to blow out in the amp? The only time I've ever seen fuse-blow issues is with low voltage (brown-outs). And sudden use of a current hog (like an air condtioner or refrigerator) usually causing the main's circuit breaker to trip --- not the unit's fuse (or breaker).

Excess VAC just causes the amp to run at higher idle wattage values. But, the amp prolly is drawing less current, under these conditions. Thanks!



Good question. Three of maybe eight sections of my home not only
blew out, but circuit-breakers did not resolve the problems.
If I can recall, these three sections were getting too much power
~ above the standard normal that delivers the 120v.
I always felt that the older conversion from two-prong plugs/outlets
to the grounded three-prong plugs/outlets was at the core.
Something was not done right.

So, my expensive equipment (of all types of items) have expensive $80
multiple outlet power cleaners, brown out & surge protectors within most rooms.

This is the reason I suggested to check Musicman's home outlets.
Usually, not a common problem, but easily overlooked. Cheers.

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Post subject: Re: Help Bandmaster blowing fuses
Posted: Thu Jul 26, 2012 5:49 am
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Toppscore wrote:
Give BIG BOY time to PLAY so he can DELIVER HIMSELF from HIMSELF


Please accept my condolences -- it's come to my attention that the moderator of the Vintage Amp Forum has banned your alter-ego "swingville" (and yes, your identity as "swingville" was confirmed by your IP address) for making the same obnoxious assclown out of yourself that you did as "toppscore" and fraudulently re-registering under an assumed log-in.

Not bad, kid......kicked off of the same forum twice. And for the same reason! The "baron" et al are still having a world-class laugh.

:mrgreen:

Arjay

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Post subject: Re: Help Bandmaster blowing fuses
Posted: Thu Jul 26, 2012 6:09 am
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Arjay, My someone's been busy. :mrgreen:



Topp: " So, my expensive equipment (of all types of items) have expensive $80 multiple outlet power cleaners, brown out & surge protectors within most rooms. "


I DO NOT recommend this for any tube amplifier. The PS built into the amp should have had adequate design to handle surges and momentary brown-outs. Most after-market accessories for this need are not designed with vintage tube amps in mind. They can actually "choke" the response and tone. And can be an issue with amp health. About the only thing I would use is a hefty Topaz Ultra-Isolator (or some such item), for areas with really noisy lines.


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