Here is a nice little explanation of rectification and smoothing. Here is one that focuses on smoothing. This and most amps have full wave rectifiers. Our 6X4 tube is a twin diode and the PT is has a center tap on the secondary. Fun fact : The first vacuum tube was a diode. Triode is [...]
Entries Tagged as 'Amp Repair'
Sidebar : Rectification and Filtering
March 28th, 2011 · No Comments · Amp Repair, calculations, Medalist Debug
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Debugging the Medalist – Hot Measurements and the Power Supply.
March 27th, 2011 · 1 Comment · Amp Repair, Medalist Debug
All the previous measurements were taken with the power off (and disconnected). Now it’s time to measure some voltages. Before we do that however we should talk a bit about the set up. You are going to want two fairly big resistors. These are very small amps (this one should put out about 5 watts [...]
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Debugging the Medalist – Part I
March 26th, 2011 · No Comments · Amp Repair, Medalist Debug
Allriiiighty then! Time get inside the Medalist and see whats up. First, the seller reported low output and loud hum. Amp is in great shape for a 44 year old amp, only the grill cloth is obviously deteriorating. Original schematic stapled inside will be a lifesaver. The only other thing of interest on the outside [...]
Now on the bench : A 67 GA-5T ‘Medalist’ Skylark
March 26th, 2011 · No Comments · Amp Repair, ebay, Uncategorized
Preamble When last we met I claimed, without evidence, that I was in possession of an authentic, original schematic for a 67 GA-5T Skylark. How could I guarantee such a thing? I took the schematic out of a 67 myself! I just bought one on ebay after all the doings with Patrick and trying to [...]
Tags: 67·Champ·class A·Fender·Gibson·medalist·Princeton·SE·Skylark
Oh what a find! GA-5T Skylark ‘Medalist’ schematic!
March 22nd, 2011 · No Comments · Amp mods, Amp Repair, Schematics
Ok. I can guarantee that this is the schematic for a ’67 or later GA-5T. This is commonly called the ‘Medalist’ styling and an example with some info is found at John Kings site. How can I guarantee that? I’ll get to that later, but for now, trust me. Full size file is almost 3 [...]
On Ebay : A Crestline Skylark
February 13th, 2011 · No Comments · Amp Repair, ebay
Occasionally, and with the permission of the auctioner (sp?), I will post a bit about an amp I see on Ebay. This is a very clean Crestline : http://cgi.ebay.com/Vintage-Gibson-Skylark-GA-5-Amp-/190500976631?pt=LH_DefaultDomain_0&hash=item2c5abe37f7
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Skylark Rebuild : Planning Stage
January 16th, 2011 · 1 Comment · Amp mods, Amp Repair, Design, Skylark Rebuid, Songbird
Two many options are presented for my simple rebuild of the Crestline GA-5 circuit.
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New Find : A Totally Different Crestline GA-5 Schematic
August 7th, 2010 · 3 Comments · Amp Repair, Gear, Schematics, Skylark Rebuid
A ‘new’ schematic for GA-5 Crestline amps has been discovered.
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Rebuilding a Skylark
November 28th, 2009 · 2 Comments · Amp mods, Amp Repair, Gear, Skylark Rebuid
Regular readers (hahaha…. I kill me) will remember that I bought two Gibson Skylarks. One of which I fixed immediately and the other sat waiting. This is a story about the other. This is a Gibson Skylark in the “Crestline” series. It is one of the many amps released with the GA-5T model number. [...]
Tags: 753397
Debugging the GA-5T : A bit hasty…
February 21st, 2008 · 1 Comment · Amp Repair
So yes, I have removed the hum, and to a large degree the amp appears to be working well, but I noticed that bass notes got kind of farty sometimes and some specific notes would warble all over. Weird… I’ll be putting the output section up on the scope again soon to see if I [...]
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