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Post subject: Re: My '68 Bandmaster Reverb now blowing fuse, GZ34 is Arcin
Posted: Wed Sep 05, 2012 9:01 pm
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That makes sense. Sometimes even the tubes guide seems too big in some tubes (Chinese), and I've felt that I would break the tubes just trying to fully seat them. I have broken some tubes away from their base, but I haven't broken any glass so far.

I just can't even imagine any scenario in which any type of amp problem would cause an output tube glass to instantly crack upon power up.

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Post subject: Re: My '68 Bandmaster Reverb now blowing fuse, GZ34 is Arcin
Posted: Wed Sep 05, 2012 9:28 pm
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"I just can't even imagine any scenario in which any type of amp problem would cause an output tube glass to instantly crack upon power up."

How about an over-voltage or imbalance, maybe cause by a Cap or the phase inverter tube? (just postulating, I'm clueless when it comes to "valves", but feel comfortable in SS electronics. Just trying to relate the two, which might not work).

shimmilou - thanks for the feedback on the Dual BiasTester-MPD™ from Amp Head, I like the price points and ease of use and upgrade-ability. But I was also looking at the one you use - Quadstage BiasPro MQ10. But what a lousy written webpage, I still can't tell what you get and don't get, how much $$ and have to buy extra from their lousy writing job. The Dual BiasTester-MPD just seems more straight forward and easier to use for a Biasing newbie.

Still looking for more feedback before I order, probably Friday.
bluesky636 and BMW2002Ti - got any Bias Tool brand / model advise??


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Post subject: Re: My '68 Bandmaster Reverb now blowing fuse, GZ34 is Arcin
Posted: Wed Sep 05, 2012 10:12 pm
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vintageguitarz wrote:
...How about an over-voltage or imbalance, maybe cause by a Cap or the phase inverter tube?...


No, an imbalance would have to be coupled with a severely over-biased tube, and would at least take several minutes for the one tube to get hot enough to possibly crack the glass. An over-voltage would also take awhile to heat up the tube, and no sort of cap or tube problem would cause an over-voltage. Good guesses though.

vintageguitarz wrote:
shimmilou...I was also looking at the one you use - Quadstage BiasPro MQ10. But what a lousy written webpage, I still can't tell what you get and don't get, how much $$ and have to buy extra from their lousy writing job...


:?:

The part about ordering seems straight forward to me. If you prefer, email Ken and tell him that you want an MQ10, how many of each probe that you want, and ask for an invoice. Ken is fantastic with support and communication. An MQ10 with four probes (any combination of 8 pin/9-pin/7591 probes) would cost $124.05

8-pin probe 8CS, 9-pin probe 9CS, 7591 probe 7591S, $29.95 each when ordered separately.
You can get the MQ10 with two probes of your choice for $84.95, or the Q10 with two probes of your choice for $62.95, and each additional probe is 19.95 if ordered with the Q10 or MQ10.

I actually have a Q10, an MQ10, four 8-pin probes and four 9-pin probes. Great for those amps with four output tubes.

From the site:
PRICING & ORDERING

Place order via Email (ken@asharpfretworks.com), and I’ll send you an invoice. No phone call orders will be taken.

Make sure your tube is listed in the “SUPPORTED TUBE TYPE”

• BiasPro 8CS, 9CS, and 7591S: $29.95 each

• Quadstage BiasPro Q10 in dual configuration (two bias probe cables of your choice): $62.95

• Quadstage BiasPro MQ10 in dual configuration (two bias probe cables of your choice): $84.95

• BiasPro PV8C, PV9C, and PV7591 - Companion Plate Voltage probe: $24.95 each when ordered with Quadstage BiasPro Q10 or MQ10 unit. $26.95 each when purchased separately

Optionally upgrade Quadstage BiasPro Q10 and MQ10 to a full quad configuration by adding two more cables (for amps with four power tubes)

• Additional bias probe cables for Quadstage BiasPro Q10 and MQ10: $19.95 each when ordered with Quadstage BiasPro Q10 or MQ10 unit. $21.95 each when purchased separately

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Post subject: Re: My '68 Bandmaster Reverb now blowing fuse, GZ34 is Arcin
Posted: Tue Sep 18, 2012 7:46 am
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Just a heads up on the JJ gz34, my JJ rectifier lasted less than 20hrs on my bandmaster reverb before it started arcing(and yes, I did re bias the amp). Keep your receipt in case you need to return. I'm curently trying out the sovtek 5ar4, $12.99 +tax at g.c., will see how this one does.

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Post subject: Re: My '68 Bandmaster Reverb now blowing fuse, GZ34 is Arcin
Posted: Wed Sep 19, 2012 10:54 pm
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socal323 wrote:
Just a heads up on the JJ gz34, my JJ rectifier lasted less than 20hrs on my bandmaster reverb before it started arcing(and yes, I did re bias the amp). Keep your receipt in case you need to return. I'm curently trying out the sovtek 5ar4, $12.99 +tax at g.c., will see how this one does.


You know while I was researching which Mfr tubes to buy for this repair/over-haul, I read a LOT of exactly the same complaints about JJ Rectifier tubes arcing out in a very short life span. Unfortunately I didn't see those recent postings until after I bought a couple new JJ GZ34's from Tube Depot, $14.95 ea. I will be hanging on to the receipt and doing a Looooong burn-in. I went with Sovtek 6L6WXT power tubes since I read some excellent glowing reviews on the newest batches.

I ended up buying the Amp Head "Dual BiasTester-MPD™" probe set for the power tubes, which has plate voltage testing built-in. The guy in Georgia makes them himself. I considered the BiasPro MQ10, which is more expensive and no Plate Voltage capability built-in.

For those watching the forum, I decided to get serious about doing my own maintenance and trouble shooting for my own amps, since I've lost my amp tech to the wilds of the NW. I picked up a used edition of "How to service your own tube amp" by Tom Mitchell, paid $20 for it on Craigslist. It's from the late 80's, the video that comes with the very lengthy manual is in VHS it's so old! But I have a VCR to DVD deck, so I copied it to DVD and then Ripped the video to a digital file to watch on my notebook. Mitchell is amazing, looked like a 80's Glam musician back then, but talked like a MIT Engineer! I learn a $@!& load just watching the 75 minute video! He covers everything, how to test power caps, filter caps, resistors, SS rectifiers, tube rectifiers, diodes, transistors, tubes, trouble shooting, speakers, wiring, EVERYTHING! Since it's from the 80's, the amps he uses as examples are 60's, 70's Fenders, Marshall's. I'm knee deep in the manual already.

Update on the BMR it self. Still uncertain what it was circuit wise, since the chassis and transformer numbers seemed to prove it is indeed an early 1968 made amp, I contacted an Amp Tech that sells Black Face upgrade kits for Silver Face Fenders. He goes by " fenderjunkie73" on EBay and has some great kits. He kindly offered to look at my numerous chassis / circuit pics. He wrote back almost immediately and said my BMR is an early 68 and a sorta rare hybrid of half Black Face and Half first edition Silver Face circuit; very desirable. Still it would benefit from his SF to BF conversion kit ($50) which turns it into essentially a BF Super Reverb. I'm considering it, unless I can find the conversion schematic/instructions and parts on my own. I'm thinking I might also convert my '70 Vibrolux Reverb I use a lot too. Anyone got ideas where to find conversion instructions and parts, like the Atom brand Caps or Caps most like the originals??

Thanks everyone for getting me hooked on this, it's like a drug .... only a lot more expensive.


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Post subject: Re: My '68 Bandmaster Reverb now blowing fuse, GZ34 is Arcin
Posted: Thu Sep 20, 2012 2:02 am
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Vint, your idea is admirable! The reality of the conversion is very extensive. I wouldn't want to discourage your effort. A $50 kit would only be the tip of the iceberg. You'll end up spending,at least, four or five times that, to do it right. If you're committed to the project, education is the foremost thing. It's not tough to understand what has to be done. But you should know why the changes are being made. The good news is that after all your effort, you'll have an intimate knowledge of the amp's workings. Art

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Post subject: Re: My '68 Bandmaster Reverb now blowing fuse, GZ34 is Arcin
Posted: Thu Sep 20, 2012 6:55 am
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That's great vintageguitarz. Educating yourself, doing your own research and using proper tools is the way to go. Keep us informed. :)

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Post subject: Re: My '68 Bandmaster Reverb now blowing fuse, GZ34 is Arcin
Posted: Thu Sep 20, 2012 7:00 pm
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aclempoppi wrote:
Vint, your idea is admirable! The reality of the conversion is very extensive. I wouldn't want to discourage your effort. A $50 kit would only be the tip of the iceberg. You'll end up spending,at least, four or five times that, to do it right. If you're committed to the project, education is the foremost thing. It's not tough to understand what has to be done. But you should know why the changes are being made. The good news is that after all your effort, you'll have an intimate knowledge of the amp's workings. Art


Yea, I'm sure if I have to buy "retail" kits and components I would end up spending 3 or 4x more to replace everything. But do I really have to? The guy did say the circuit is already 1/2 Super reverb (which I've already 1/3 verified by comparing the 65 SR schematic to the BMR AA768 schematic and variances on my actual circuit board that matches the SR and not the BMR. But if I could find, or if someone knows of a "Paper" on what to change and how to do the mod, it would save me a ton of time and "experimenting". I mean I could just unsolder everything and completely remake it using a 65 Super Reverb schematic (besides, I already own a 64 and 65 Super Reverb), but what if that's not necessary?

I've never owned one, but I've read that originally the BMR was supposed to be head only version of the Pro Reverb. Not familiar with the Pro reverb sound vs the SR sound, I'm not sure I want to go there. Anyone have opinions? Frankly, I'd rather have a "head only" version of a Twin Reverb!

If anyone knows of a thread or online story on this SF to BF BMR mod, please chime in!!


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Post subject: Re: My '68 Bandmaster Reverb now blowing fuse, GZ34 is Arcin
Posted: Fri Dec 28, 2012 7:28 am
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Hey had to bump this tread

any new news ?
My 68 Bandmaster Reverb came with a Mullard GZ34 and has yet to cause any troubles.
Then I bought a wholesale lot of tubes from a local university with yet another RCA branded Mullard ( nice spare to have) !

Just wondering what the outcome of new tubes was

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Post subject: Re: My '68 Bandmaster Reverb now blowing fuse, GZ34 is Arcin
Posted: Fri Dec 28, 2012 7:38 am
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Hey! This is supposed to be a time for joy, not for rubbing it in. :lol: JK!

I am curious as to the outcome too. :?:

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Post subject: Re: My '68 Bandmaster Reverb now blowing fuse, GZ34 is Arcin
Posted: Fri Dec 28, 2012 6:40 pm
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Sorry Shim !

Had an offer on the Bandmaster and a Bassman head in the wings, just couldn't do it !
The fella bought my 75 Vivro Champ instead

The Egnater Rebel 20 had taken its spot on the practice room so........

The reverb on the Bandmaster and the fact that it's basically a blackface in a silverface cab makes it a tone monster and worth hanging on to.
I don't find the smaller OT to be that big of a difference to the Super Reverb or the two Blackface Bassman heads I owned.
I did pull V-1 and use the reverb tremolo side only.

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Post subject: Re: My '68 Bandmaster Reverb now blowing fuse, GZ34 is Arcin
Posted: Fri Dec 28, 2012 7:44 pm
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Yeah, I tried pulling V1 from my Bassman and it made the normal channel a little more crisp and distorted, and although a cool sound, I didn't quite like it as much because I want as clean a sound as possible so I put the V1 tube back in.

What about the OP and his amp, wassup? :?:

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Post subject: Re: My '68 Bandmaster Reverb now blowing fuse, GZ34 is Arcin
Posted: Sun Dec 30, 2012 6:21 am
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Looks like the OP didn't stay with us

Way off topic but I picked up a 1955 Grundig 3035 Tube radio yesterday at an auction, cleaned up the tube sockets and rerouted the antenna and it works !
Sounds pretty darn good too

Man I love old tube technology ! the power tube is a Valvo EL84

Looks too cool in my practice room too :mrgreen:

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Post subject: Re: My '68 Bandmaster Reverb now blowing fuse, GZ34 is Arcin
Posted: Sun Dec 30, 2012 7:20 am
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Very cool, and it is a vintage amp. :wink:

I recently fixed up this one, only needed a can cap. Tubes work fine and it's very quiet, no noise. It picks up several stations quite clearly, AM only of course. Listening to talk radio in the morning while drinking coffee is like a trip back in time.

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Post subject: Re: My '68 Bandmaster Reverb now blowing fuse, GZ34 is Arcin
Posted: Sun Dec 30, 2012 7:45 am
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I'm shocked at how good the FM reception is with this one !

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Cant get international stuff, however I picked up a few Ham guys that sounded American :lol:

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VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


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