New 180W Clone (Converted Fender)...Oscillations, darn, darn

[ic-racer]

Here is my 12v relay/LED power supply board made with the gray fishpaper. The layout is not very logical, but I had to put the caps at the far end of the board because it is a tight fit in the chassis.

Also shown is the proposed location of the 12v transformer. For all the room in this chassis, it was a close fit. I really did not want to mount this thing in a place where the 120v AC input to the transformer would be near any thing but existing power supply components.

[ic-racer]

Got it all wired up today. Sounds good, but the controls need fine tuning (ie pot values etc).

Here is what it wound up being:

*Fender Tone stack modified like "Cool Mod for the Normal Channel" layout from Schematic Heaven.

*Jazz/Rock switch

*Deep Switch

*Mid Boost Switch

* Original Pull/bright intact

* OD switching with relay/foot pedal/LED. When foot pedal is not plugged in, can be switched on/off with the amp's original 'distortion' switch. This required "OD=Relay ON" rather than "OD=Relay OFF", but I don't think this will be a problem.

* PAB switching with relay/foot pedal/LED

* Reverb bypass switch

More pictures to follow...

[ic-racer]

A little trouble shooting and it is all sorted out;

* Mid boost switch upside down
* OD relay rewired from "OD=Relay OFF" to "OD=Relay ON"
* No ground to OD Level & Ratio pots (fixed:oops:)
* B+ too high (one less tube section than original; cured with a dropping resistor to ground; B+ from 340v to 270v. V1ab&V2ab now about 194v from 224v)


I was waiting on an order for a second 'stereo' phone jack for the distortion/PAB pedal (two stereo jacks & ground = 5 pin jack). The pedal I am using is a standard Fender jack with two plugs. I was surprised to find the amp has one stereo jack and one mono isolated jack. With this isolated jack I can use :

Jack 1 (mono isolated ground)
PAB LED POWER to jack 'ground'
PAB RELAY POWER to jack 'tip'

Jack 2 (stereo grounded)
OD LED POWER to jack 'ring'
OD RELAY POWER to jack 'tip'
GROUND to jack 'ground'


The foot pedal itself comes with a DPDT and a SPST. I was planning on making it two DPDTs, but after reading a post by Gil, it looks like I can use the SPST since 'LED ON' and 'RELAY ON' will be the same.

[ic-racer]

Some pictures of the 'so-far' finished amp.

Except for the replacement of the EQ knobs with mini-toggles, the amp's appearance and function of the controls is nearly like the original.

Except for poking holes and placing eyelets in one of the original backing boards, all the mods are potentially reversible (but I'm never going back on this one !)

[ic-racer]

I failed to mention that I also put an extra 20uf cap with a 1k power resistor on the new board to add a separate B+ for V1. As the amp came from Fender, all three preamp tubes shared the same B+.

Here is another picture showing the way I used the original foot pedal jacks for the OD and PAB.