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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Tue Aug 30, 2016 10:44 am
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Very interesting. I have not seen a guitar amp speaker (except beaucoup bucks JBL, Altecs, and EV) with redone permanent magnets. Pretty hard to get the alignment ok, so that the voice coils don't seize-up. Esp when pushing the speakers with lots of watts and bass.

You have any photos of the fixes? Thanks!

:)


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Tue Aug 30, 2016 11:10 am
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No, but since you asked. I'll take it out and snap a few.BRB
Best picture my cam would take of the label. It can be seen better using the zoom function on the auction house picture on page 1 of this thread.
Image
Image
Image
Image


Last edited by sfceric64 on Mon Jul 10, 2017 10:41 pm, edited 1 time in total.

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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Tue Aug 30, 2016 3:02 pm
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I don't think that magnet assembly has been tampered with.

Arjay

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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Tue Aug 30, 2016 4:12 pm
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Retroverbial wrote:
I don't think that magnet assembly has been tampered with.Arjay
Really, I thought for sure yes by the looks of it. Doing the math, then it is only 12 watts given the 20w p12r has a 10oz magnet and explains the problem of not handling the awesome power of the TV deluxe @ about 13 watts.

Back to the c12k option for a second, I would have had to modify either the baffle or the speaker ring to get it to mount. I tried every hole it would not line up, I wonder if all the new re-issues are spaced for a trouble free fit to a 4 stud baffle.

I have been stewing over the unbalanced 6.4vac @ pin 2 on the recto-frier. Can I detach that leg off the pin and cap it and jump from pin 8 to give 4.9vac for a better balance to the rectifier filaments?

Thanks


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Tue Aug 30, 2016 4:54 pm
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I don't think that P12R packs the beef to handle the amp's output. Were it mine, I'd seek out a post-1958 P12Q or P12P. They're rated for 25 watts and 30 watts respectively.

Arjay

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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Wed Aug 31, 2016 4:40 pm
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Doing what I hoped I wouldn't have to for circuit stability, bye-bye CC 250k resistors. For now at least....


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Wed Aug 31, 2016 5:50 pm
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Are you replacing them with metal-film/metal-oxide types?

Arjay

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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Wed Aug 31, 2016 7:50 pm
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Retroverbial wrote:
Are you replacing them with metal-film/metal-oxide types?
Yes, that's all I have on-hand metal-oxide. Also changed the 250ohm 5w to a sandbox style. I still haven't figured out the P/T secondary issue yet either, still to much juice to one of the recto-filaments.

My B+ didn't change 386 next drop was 292 and next was 270 (both decreased about 20).
V4 plate is 364 was 363
V3 plate is 365 was 363
V2 is 173/172 was 170/166
V1 is 88/93 was 88/89
(I didn't change the 2-5m cathode-grid{although 1 is out of spec} resistors or the 2.5k & 7k or the input resistors)


Last edited by sfceric64 on Wed Aug 31, 2016 10:01 pm, edited 1 time in total.

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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Wed Aug 31, 2016 9:42 pm
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It's possible that the asymmetrical heater voltage at the rectifier is merely inherent to that particular P/T. If so, there's only so much that can be done to equalize it -- might be more trouble than its worth.

Arjay

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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Wed Aug 31, 2016 9:56 pm
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I see, I suppose I'll find out if its a rectifier killer soon enough. I did read on the Triad historical site that it is not intended to be used as a stand alone leg, not much detail. Not much else I could find there, no serial number history just model #'s and specs from about 1950-present. They started sometime around the early 40's I think but no records from those days. Mine is numbered just 50 more than the 46' Champ 600 listed on the other thread about the oldest amp by BMW.


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Wed Aug 31, 2016 10:23 pm
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Hate to see you put a vintage 5Y3 at risk -- do you have a modern-made (ie: a cheapie) rectifier that you could substitute?

Arjay

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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Thu Sep 01, 2016 9:17 am
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No I don't have any modern valve 5y3's, maybe I'll swing by the GC and pick one up this weekend. I'm still using the one that was in the amp when I received it, that wonky looking one is still kicking butt. And I have a 5y3wgta in reserve. Gonna plug in here after lunch and put a little time on the fresh components and then re-check the numbers. All the 250k resistors, measured about 300k or higher and one was 251k1w(extra band) but just wanted same look/wattage.


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Thu Sep 01, 2016 9:57 am
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sfceric64 wrote:
All the 250k resistors, measured about 300k or higher and one was 251k1w(extra band) but just wanted same look/wattage.


That's pretty significantly out-of-spec, significant enough that I would replace them. Tolerance for components such as those should be 10% (silver band).

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Thu Sep 01, 2016 11:16 am
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I wouldn't get a modern 5Y3GT. There are plenty of good US made ones still available. Even, as spares...

http://www.ebay.com/itm/NOS-NIB-GE-5Y3G ... SwdIFXxcAS


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Thu Sep 01, 2016 12:26 pm
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BMW2002Ti wrote:
I wouldn't get a modern 5Y3GT. There are plenty of good US made ones still available. Even, as spares...

http://www.ebay.com/itm/NOS-NIB-GE-5Y3G ... SwdIFXxcAS


I recommended a cheapie merely because if it became a crispy critter due to a possible P/T problem, it wouldn't be a major loss.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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