? re: #124

[Pete]

OK, thanks for your indulgence on this.

I've learned much from studying the #124 pics and reading all about them here.
I was recently looking them over again and find I have accumulated a few questions that I'm really curious about.

So at this time I would like to throw out the list for any remarks anyone would care to make

1.) Is that a mistake on the drawing or does the wiper of the Master Vol really go to the input of the PI? (as shown on the drawing) IOW, is the master before or after the loop jacks?

2.) Is that just a standard Twin style replacement OT? In some of the pics (21, 22 & 23) it looks a bit larger, covering most of the space between the 6L6 and the front panel. That would make the (mounting) hole spacing more like 4.25 not 3.5 in. (front to back)

3.) What do the numbers on the blue sticker (OT) mean?

4.) Can someone tell me what the number would be for the diodes used for the main (B+) rectifier?

5.) Is there any technical reason for the size and/or type of resistor used for the neg feedback? (that one seems to be in all amp pics)

sorry if any of this was covered, but I don't think I missed it.

Please comment at will, much thanks.
Pete

[Normster]

I'll venture a few guesses...

1.) Is that a mistake on the drawing or does the wiper of the Master Vol really go to the input of the PI? (as shown on the drawing) IOW, is the master before or after the loop jacks?

My best guess is that it goes to the preamp out. The master has a brown wire coming off the wiper and it looks like it runs under the board to the jack. The PA "In" jack has a green wire running under the board and looks like it goes to the PI input.

2.) Is that just a standard Twin style replacement OT? In some of the pics (21, 22 & 23) it looks a bit larger, covering most of the space between the 6L6 and the front panel. That would make the (mounting) hole spacing more like 4.25 not 3.5 in. (front to back)

According to the stamping, it's a Fender 022889 which is a Twin/Twin Reverb transformer

3.) What do the numbers on the blue sticker (OT) mean?

First two numbers appear to be Primary and Secondary impedence measured in Henries. Third number is the turns ratio. Fourth number is the primary resistance.

4.) Can someone tell me what the number would be for the diodes used for the main (B+) rectifier?

Someone can, but not me.

5.) Is there any technical reason for the size and/or type of resistor used for the neg feedback? (that one seems to be in all amp pics)

I may be coming into some 2 watt carbon films in the near future. I'm going to try one and see if I can hear a difference.

OK, now that I've made a fool of myself, where are the experts?

[Bob-I]

The diodes look like standard 1N4007 to me, but I wouldn't swear to it. I agree with Norm on the 2 watt carbon film. My guess is that HAD used it because he had it. There's no technical reason for a resistor that big in that location.

[Pete]

Thanks for the replies.
The reason I question the diodes is they look bigger than a 1N4007.

I thought the master should be before the loop as in most schems. I guess that is a mistake on the drawing, we know there are some others.

I asked about the transformer because I've been using an OT that looks similar to that one but is a little smaller I think. I can't remember where i got it but it was new and I always thought it was for a twin. It has 2 secondary taps with black, green and yellow leads (4 & 8 ohm I guess). It has the number 0990775 and the word Fender stamped on it and the primary measures about 73 ohms resistance. Is this suitable for 4 6L6s?