Ran out of time to dedicate to this project I had a 5 day gap between my other work and was hoping to get further on this project.

I have altered the preamp switching curuit so that the channels can be selected. However, after a few more hours of tracing around, i think i have tracked down a possbile grounding issue on the effects board.

Turns out the switch was stuck on ground, not stuck on open. I altered the switching curuit to work, but afterwards found out that it wasnt acually the switch! that is when i traced it back to the fx baord-
Now my inbox has been re-flooded with alternative fuel research needs. Im not done! but by progess will be much slower from here on out.

^^ my mistake- prob wont get more then 2 watts from the lm386

The switch has been repaired! all swiches are now working properly and all channells are avalible for use! so we have conquered the first problem on this laney. With the switching curcuit repaired, its time to move onto the hum.

This hour's developments....

Im going to call the node of d3,r9,r10 Node 1 for this post

There was a bulky soldeir joint close to node 1 that was just slightly touching it. This bulky soldier joint was a ground point, and thus Node1 was permently groudned=> this explains perfectly why i was stuck on the clean channel! So i got out my exacto-knife and gently cut the connection between node 1 and the bulky soldeir. Wala! Node 1 now had a 5v reading! this in turn swapped the values for A and B with the result of making the gain/drive channel active.

switching between the gain and drive works correctly. Those were the C and D values going to ts6 and ts8. Not at the end yet though. Now im stuck on the gain/drive channels. but i know why before i even start to look.
Heres the logic-
When node 1 was perm grounded, it was on the clean channel. after the fix, Node 1 is perm ungrounded, and stuck on the gain/drive channels. Makes me think the Channel switch (labeled clean/drive and is just to the left of node 1 on the schematic) is not working properly.
Thats where i am now- next move is to wrap my head around that switch.

Im looking at how the values from cd4069 correspond to the fets. Based on the schem note that "switching fets. high gate V = off" it seems that some of the fets are "stucK" off. There are several places on the cd4069 with const high or low V.

On the right side of the schem at the top (below the chip diagrams) there are 4 transistors (pf3820). each one is associated with a,b,c, or d. These are points from the switch curcuit we have been exploring. Based on what im seeing, A is has a const Low V, and b,c,d have const high V. It would seem that the 3 of these transistors that have high V are stuck off, and they seem to be the ones associated with the drive/gain states. the 4th, associated with A is stuck on, which seems reasonable to my eye.

The huge assumption i made was that pf3820 is in fact a switching fet. If im reading this right, would that point to a bad cd4069 chip?

was taking some more V readings, and some of the pins do switch from "high" to "low" and vise versa when switched. The only 2 pins of note where 2 ,9, and 13. Pin 2 had a const V of .1 regaurdless of switch pos. and pins 9 and 13 had a "high" of only .8v  (low of 0).
The rest of the pins that did switch V went from 0->17 or 17->0. Some pins had a const V of 0 or 17.
You have inspired me to thourghly inspect this area today.

could use a lm386 ruby- Ive prob put 3 or 4 of these together for various uses over the years.

http://runoffgroove.com/ruby.html

I have followed that schemataic with success using 9v or 16v supply.

thanks for the feedback. I checked out the datasheet for the cd4069, got the V and heres the results

1- 17
2-.1
3-0
4-17
5-17
6-0
7-0
8-17
9-0
10-17
11-0
12-17
13-.7
14-17

i could record the V on each lug for different swtich postions if that would help-

as for the LED indicators... i think i have located 2 of them. to the right of u2-d... it seems to be assumed to be between p10 and p11 right above where it says "drive 2"
also right below that, between p8 and p9. Thats where the LEDs acutally are when I follow the wires.

here is a lm386 ruby tucked inside of an altoid tin

about 1/2 way down on the right of page 3 of the shematic you will see r54 and r53 (they will have the FP fire proof label on them). These are the resistors that I said were running hot

Directly to the left of the resistor their are caps c34, c35. These caps are rated 16v. I am reading 17.5 V and am considering replacing them with higher rated caps.

attached is the PDF of the schematic-

Picked up a Laney tfx 320. Trying my best to troubleshoot it, was hoping for some more ideas to throw into the pot.

This amp is Tube pre-amp with solid state main. The tube is a ecc83 (similiar to the 12ax7)

PRoblems: about 3 sec after turning on, it begins to hum. The hum stays consistant as long as the amp is on. none of the controls effect this hum.

The amp still functions despite the hum. The main volume/high/mid/low controls work. BUT, the preamp seems to have no effect. none of the gain/drive conrols do anything, and also the LED's that indicate drive/gain stages do not light up.

Heres some thins ive looked at already:
1: All fuses are fine- double checked them all
2: Annode/plate voltage for the tube is at 317(max) which is below the max rating for the tube
3:tube heater V are 13v (high, but shoudl be fine)
4:tube hums the same with or without the tube (pulled the tube to check this)
5:drop resistors on the preamp baord run very hot. They are 2x 470 5w. They are part of the curcuit that takes 50v ->drops/filteres to 17v for preamp board supply.


My next move will be to replace the filter caps on the pre-amp. The current filter caps are only rated 16v, while it seems 17.5v are present. This will require me to totally dissasemble the amp to reach these compents.
Before i dive in i wanted to see if anyone here had some ideas. Any little quick check or extreme idea you can think of will be appreciated.
I do have a schematic of the amp. could post a link to the PDF if anyone would like to see it.

If there is any other information you need to assist your thought, let me know and ill post it for ya. Thanks for reading.

Thanks for the replys- they got me thinking more clearly about what i was looking for

1) The transistor I was speaking of before was a j175
datasheet-- http://www.datasheetcatalog.org/datasheet/philips/J174_175_176_177_CNV_2.pdf

I was taking voltage measurements from the "gate"
the V would increase from 0-42v < 1 min after turning on

2)took your advise and traced from the trans. to the source and found a resistor and a diode.
4M ohm resistor and a 1n4 148 diode (in parrallel)
These had a constant 46V going in with (increaseing) 0-42v < 1min going out

I replaced the diode and resistor with new parts (didnt help or hurt anything)

3) lm317 voltage regulator--
http://www.datasheetcatalog.org/datasheet2/1/03cgthpfat4t4ly5kfp5lpwladfy.pdf
I happend to have one of these laying around so I placed this into the curcuit before the diode resistor set. (so that the output of the lm317 would go to the input of the resistor and diode--> that would go to the transistor gate)

I set the regulator to 40v (using the formulas in the datasheet to choose R1 and R2 i think I used r1=240 and r2=6.8k ohms) I feel as if i jumped over the real problem, but I have the Voltage ceiling I want where i want it (remember 41v+ was overloading the transistor and causing terrible noise)

I tested for a while and found all the controls work fine. The regulator works and never allows more then 40v to pass. The output V of the diode and resistor maxes out around 39V and that goes to the Gate of the transistor.

4- i Emailed Crate and asked for schematics- It seems like i can get one from them if i fill out the correst waiviers. It may take some time, but would anyone like a copy of them if i can get it?

This post is going to lack some proper terms and many saftey features but....

i got out my multi meter and began testing everything i could get my tips to touch. There were 5 Jfet transistors in the area that i thought was the preamp. all but one gave similar readings with the amp on and off. The last FET showed the following...

amp turns on- V= around 20v
this slowly increases to around 42v and the "noise" begins
so i placed a 10Mohm resistor between the 2 lugs that had the increasing voltage.
this stabalized the voltage to around 36V (below what seemed to be the cutoff for noise)
What im trying to do now if figure out what realy is wrong. what i tried to explain above was just me throwing ideas all over myself looking for clues.
My first move is going to be to remove the FET and replace with a new one- then work from there.

I have a Crate GFX 30 solid state amp I'm having a problem with. After it is on for like a min it makes this white noise.(like the static sound of a "snow" tv channel). You can play through the amp before and after this happens. When you turn the amp off and then back on right away, the noise stops, waits another min, then starts again.

I cant find a schematic for this amp. (would realy appreciate having one)
I can post any other info you may need.
some basic onfo on the amp
http://www.crateamps.com/pdf/manuals/GFX30_OM.pdf

Thanks for any input