Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Big chief on July 02, 2017, 09:12:43 am
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Have Guild Masteramp early model with 50L6 tubes
Looking for some one to repair
If not violating policy would like to have name and email address of repair person
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What state or country do you live in?
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I live in St Pete Florida can ship to you
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Contact plexi50. He does a lot of repair work in the Tampa area. I think he's actually in Clearwater.
http://www.triodeamplification.com/ (http://www.triodeamplification.com/)
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If Plexi50 is unavailable, I live about an hour n 20 min. south in Venice.
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Ciao Punkykatt
I live north, ~30Km far from Venice
:icon_biggrin:
Franco
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> with 50L6 tubes
This is almost certainly a transformerless "death trap". Under certain conditions it can be deadly. It NEEDS an isolation transformer before any work starts.
If just two 50L6, 65VA will do. This is a large lump, mount it in the bottom.
> plexi50 .. punkykatt .... Franco(??)
You guys be sure you know what you are doing. The amp NEEDS that isolation transformer or it is deadly even to touch. The amp is practically undocumented, and strange power supply. This is not just another DeLuxe re-cap job.
There is a MEF thread that runs 42 messages just trying to get power up in one of these things. http://music-electronics-forum.com/t40364/ (http://music-electronics-forum.com/t40364/)
The Selenium rectifier(s) are a toxic-stink waiting to happen.
Here is what a properly restored Guild should look like inside:
http://www.letstalkguild.com/ltg/showthread.php?178813-55-Masteramp-66-interior-chassis-photos-%28lots%29 (http://www.letstalkguild.com/ltg/showthread.php?178813-55-Masteramp-66-interior-chassis-photos-%28lots%29)
Remember that the Guild amplifier side-product was low-low-low-cost, so the designs changed with the parts market, even within the "same model". They also ran into tightening UL requirements about shock leakage, so many obscure changes in the power system.
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http://el34world.com/charts/Schematics/files/guild/guild_masteramp_1959.pdf (http://el34world.com/charts/Schematics/files/guild/guild_masteramp_1959.pdf)
Hmmm. Schematic shows power transformer , 5AR4 rectifier, 2 6L6`s. Are you sure you this amp is a Guild Masteramp?
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There are several versions of the masteramp. The schematic in Doug's library is not the right one.
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> plexi50 .. punkykatt .... Franco(??)
You guys be sure you know what you are doing
"My" Venice is in Italy not in the USA :icon_biggrin: :icon_biggrin: :icon_biggrin: :icon_biggrin: :icon_biggrin:
it was only a joke
Franco
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I have done perhaps 4 or 5 of the transformer less amps. I have been using the isolation transformers available from Mouser Electronics. Safety is the utmost importance.
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> sure you this amp is a Guild Masteramp?
It appears that Guild used "Masteramp" the way Mercury used "Cougar" (happy 50th birthday!). They put the name on many different things. The '67 Cougar was a stretch Mustang. 1974, Cougar was a Torino, which by now was a cut-down 1965 Galaxie (full frame). 1977 even saw a Cougar station wagon. 1980 it got on the Fox (Zephyr, Capri) platform. 1983 the badge was moved to the new improved Thunderbird platform. 1989, a different Tbird base with IRS; you could still get the Windsor 305 V-8 (now called 5.0). 1999 the cat moved to the Probe platform with I-4 and V-6. By this time nobody knew what a Cougar was, the badge died in 2002.
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Really takes some balls to call a 50L6 amp the "Masteramp". :l2:
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The *six* 50L6 form should be competitive with two old-recipe 6L6.
Two 50L6 is a very large table radio.
Price was probably decisive. At some point the cheap 50L6 were fading, and two 6L6 became acceptable to the bean-counters.
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thanks
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2x12ax7s, 1x6sn7 (for the trem), 2x50L6gt, 1x35z5 recto. that's what you have. This one looks like it has the 6 volt filament tranny but not the power tranny .Probably the Model 66, not the more common 66J, which was a 6V6 model. The earlier Masteramp Model 60 had a power transformer and a 6 Volt filament transformer. I have two of them and a buddy has a third. These are small cabinet amps with an RCA 12 inch speaker.
Masteramp was the name for the amp line.
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thanks
This particular cabinet was used on quite a few different model. I have one with 6x50L6gts, and two that have pairs of 6L6gts. I have another with 4x6v6gts. They all share the 6SN7 for the tremolo. Around 1958, Guild moved to a tweed/ brown cloth, then, around 61 or so, changed to a blue tolex. Also around 58, the 6SN7 was replaced by a 12ax7 for the trem and the tube lineup stabilized into 6V6, 6L6 and later, 7591s. 6gw8s were used on the lowest priced models.
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https://www.youtube.com/watch?v=Eo5VKsFUA6Q (https://www.youtube.com/watch?v=Eo5VKsFUA6Q)
My buddy's early Masteramp with the factory power tranny. I actually prefer the OP's amp, because there is a lot more real estate inside. I am looking for one of OP's amps to round out the fifties models I have.