Guild Masteramp (Tweed?) Schematic Help

[dorrisant]

First, pic is the mica cap on input jack 4.
Then pics of the top of the board and then the bottom showing all the othe mica caps.

Note some of the components are lifted from the board for testing. I tried to push them back to their associated terminals for the sake if the pics.

[dorrisant]

To go along with the next post...

[dorrisant]

Here are some reference pics of the chassis.

[dorrisant]

Some pics of the power supply and power tube section.

Default, I put a B+ marking next to pin 8 on V4... V4 & V5 pins 8 are tied then go to one section of a 5uf-5uf-5uf cap via a 150ohm power resistor then to one of the terminals on the orange selenium rectifier. Also there is a wire from V4-8 that goes to the large multi-section cap directly above the strength control pot. I can't see the shapes that should indicate what value the wire is tied to but is is the one at the 12 o-clock position in the pics. Maybe Robert can see what this is connected to..? Post a pic from your amp maybe...?

As far as labeling the schematic with a name for credit... I was thinking when we are done we could all put our names on it and let everyone enjoy the benefits. Group effort - Group credit!

Tony

[dorrisant]

More pics of the PS...

Martin, so glad to have your expertise applied here. Thanks a bunch, makes me feel a lot more comfortable!

Default and Straight8 - please post any pics you can that may help clarify what we are seeing.

Btw, I'm not trying to run up my post count. My phone will only let me post five pics at a time with this resolution.

Tony

[martin manning]

Here's the info you need to read the molded caps: http://www.tpub.com/neets/book2/3g.htm Looks like you have two types of codes there, the solid arrow and the broken arrow.

[Default]

Some pics of the power supply and power tube section.

Default, I put a B+ marking next to pin 8 on V4... V4 & V5 pins 8 are tied then go to one section of a 5uf-5uf-5uf cap via a 150ohm power resistor then to one of the terminals on the orange selenium rectifier. Also there is a wire from V4-8 that goes to the large multi-section cap directly above the strength control pot.

[img:360:246]http://www.radiomuseum.org/images/tubee ... altung.png[/img]
Pin 3 should be connected to the output transformer
Pin 4 is the screen and goes to the B+
Pin 5 is the signal grid and should have a resistor to ground and a cap from the last gain stage.
Pin 8 is the cathode of the 50l6, so the 150 ohm should be grounded and the cap should be the bypass... Is that terminal on the rectifier a ground terminal??

[dorrisant]

Here you go...

Note: I cleaned the area of the chassis around the footswitch jack. This is not isolated, it is chassis grounded. Mine looked to be isolated until being cleaned.

Tony

[Straight8]

Not sure if these pics will help or hurt. As you can see a lot of components have been swapped in mine. I pulled the big multi can caps and wired in new modern caps in the back. Resistors that seemed to have drifted a fair amount were swapped out too. Anything suspect went. All of this work was done nearly 8yrs ago so I'm little fuzzy on some of the details. But ... in the end, it works!

[dorrisant]

Pin 3 should be connected to the output transformer
Pin 4 is the screen and goes to the B+
Pin 5 is the signal grid and should have a resistor to ground and a cap from the last gain stage.
Pin 8 is the cathode of the 50l6, so the 150 ohm should be grounded and the cap should be the bypass... Is that terminal on the rectifier a ground terminal??

Pin 3 - yes
Pin 4 - yes
Pin 5 - yes
Pin 8 - I think it is using the 150ohm resistor and 20uf cap from MC1 in parallel... Maybe?

[Default]

That sounds right. I was a bit confused. It happens a lot.

[dorrisant]

Ok... After looking at Robert's pics I noticed what I have labeled as the three 5uf/? are actually three .05uf caps in a can with common negative on the shell. Never saw one of these before and I couldn't see the decimal or zero either...

So that changes things... Thanks for the pics Robert!

Tony

[martin manning]

Tony, here's how I see the the power supply and the power tubes based on your drawing. The small selenium rectifier seems to be for the screen supply, but I can't make sense of the orange selenium rectifier or what it supplies power to. Sorry about the poor quality pic.

[dorrisant]

Martin,

Well... Pin 5 of the rectifier is connected to the bottom terminal of the orange rectifier and also connected to the 80uf positive (+) can cap. The top terminal of the orange rectifier is connected through a 10ohm resistor to the negative (-) of the multi-cap can labled MC1.
Pin 2 is connected through the 100ohm resistor to the small rectifier negative (-). Pin 2 is also connected to the negative (-) of the above mentioned can cap as well as one side of the AC and filament tx. The positive (+) of the small rectifier is connected to V5-4 and V4-4 and filtered by the 80uf of the multi-cap can MC1.

Also, the negative (-) on neither the single cap can nor the multi-cap can are not connected to the chassis. Both are showing about 40k to the chassis. There are very few wires to the chassis ground as well as all of the pots and jacks.

Weird too, the bypass switch grounds out the signal at the output jack to the chassis. I don't think I've ever seen that before.

Sorry if I'm confusing you. I've never had to work with a supply like this... so your help is much appreciated!

Tony

[dorrisant]

Here's the info you need to read the molded caps: http://www.tpub.com/neets/book2/3g.htm Looks like you have two types of codes there, the solid arrow and the broken arrow.

Does this look right?
510pf mica 20% for the first pic, 1000pf mica 3% for the second pic.[/code]