Paleo-Electronics

Clueless Idiots and High Voltage Vacuum Tubes Really Do Mix!

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Entries Tagged as 'calculations'

Songbird : Choosing The Output Tranny

June 5th, 2011 · 1 Comment · calculations, Design, Songbird

Actually, it is already chosen. It is the existing 8k:8 center tapped primary that is already in the Crestline amp. However, I am excited by the choice, and at the risk of sounding like a dangerous lunatic, I’ll explain why. First though, lets look at a standard SE output section. That’s from a late 50’s […]

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SongBird : Output Tube(s)

June 3rd, 2011 · No Comments · calculations, Design, Songbird

6AQ5 That was easy! Ok .. moving on.. Wait.. What’s that you say? You want to know why? Really? Well, alright.. if you are that bored.

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Sidebar : Graphing Resistances

May 22nd, 2011 · No Comments · Amp Repair, calculations, Datasheets, Schematics

I want to talk about the power section of my Medalist in detail (and some other things), but before I do that I’m going to give myself a refresher course on tube data sheets and graphing resistances. Recall, if you will, that V = I * R.  An equation in three variables.  If any one […]

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Debugging the Medalist – More Weirdness

April 23rd, 2011 · No Comments · Amp Repair, calculations, Medalist Debug

So I replaced the bad resistors and took so measurements. Basically, everything looks perfectly reasonable, and it sounds great at low volumes, but I have one major problem. Anywhere past 3 or 4 on the volume knob slams the output tube with up to 30 V (rms) on the grid! For reasons I may show, […]

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Debugging The Medalist – The Output Tranny

April 7th, 2011 · 1 Comment · Amp Repair, calculations, Medalist Debug

Well, the parts have arrived, but first, I want to understand that output section a bit better so let us examine the OT. The always helpful Patrick at Mercury Magnetics suggested that the drop in replacement they make is the GA5-0 which has an 8kΩ primary to 8Ω secondary. He also noted that they varied […]

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Debugging the Medalist – Intelligent Design

April 5th, 2011 · No Comments · Amp Repair, calculations, Medalist Debug

As we now have some reference voltages to use (see previous post) we can take a lot of the guesswork out of our debugging. So here is the power section from the Master Service Manual. Those are design values. The test readings are in the top corner of that page (319 in the MSM) and […]

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A Tale of Two Schematics

April 4th, 2011 · No Comments · Amp Repair, calculations, Medalist Debug, Schematics

In the course of working on two different 5T ‘Medalist’ Skylarks, we have come across two different schematics. One of them came from blogfriend Patrick and is found in the 1966 publication of the Gibson Master Service Manual. The other was attached to the amp I bought. Here is the one I got : Here […]

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Debugging the Medalist – What Happened?

April 3rd, 2011 · 1 Comment · Amp Repair, calculations, Medalist Debug

I don’t really know what happened. My suspicion is that the tube blew, but the other possibility is that the cathode resistor blew, causing the tube to blow. Again it could very well be the 44 year old original tube and I might well be the first guy to run it for a long long […]

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Sidebar : Rectification and Filtering

March 28th, 2011 · No Comments · Amp Repair, calculations, Medalist Debug

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 […]

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A Little Status

May 3rd, 2009 · 1 Comment · Amp Computer, calculations, McTube, Songbird

Since I am failing to complete numerous tasks at once, I thought I would describe their status Amp Computer The problem here was banana cables.   At some point, the ‘Asshole Audiophile’ community got a hold of banana connections and now it’s damn near impossible to get banana cables at a reasonable rate.   I wanted to […]

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