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Messages - g1

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1


R24 = NPN = C-B=0.560 / B-E=0.575 / C(N)-E(P) = OL / C(P)-E(N) = 2.11 = dead


Not sure why you are calling it dead?
2.11 is higher than many meters will register on diode function, lots of meters would call that 2.11 reading 'OL'.

Are any transistors you listed as bad giving readings significantly lower than .500 for any junction?

2
You are correct, the pre-set only works in conjunction with the footswitch.  You can plug an extra cord in that preset footswitch jack and short out tip to sleeve to see how it works.

A good place to start with troubleshooting is with power supply DC  voltages.
Looks like there are 12V, 36V, and 136V supply levels.

3
Amplifier Discussion / Re: Peavy Rage 158 no sound after 1-5 mins
« on: June 20, 2019, 01:46:19 PM »
How about resistance of R44 to ground?  (try both sides)

4
Amplifier Discussion / Re: Peavy Rage 158 no sound after 1-5 mins
« on: June 20, 2019, 12:10:20 AM »
How about checking resistance from heatsink to each of the IC pins.  The only one that should be low resistance is pin 3.

5
Amplifier Discussion / Re: Peavy Rage 158 no sound after 1-5 mins
« on: June 19, 2019, 04:24:53 PM »
Can you check same with the board fully mounted?

6
Amplifier Discussion / Re: Fuse or resistor?
« on: June 18, 2019, 09:43:02 PM »
There is a temperature dependent resistor connected to the base of the Tip30, if that is what you mean.
Where is the mystery part connected to on the schematic?
That green coating looks like heatshrink, cut it off and see what is under there.

7
Amplifier Discussion / Re: Peavy Rage 158 no sound after 1-5 mins
« on: June 17, 2019, 12:09:52 PM »
Check with meter set to ohms, lowest range.  Across D10, with it in circuit.

8
Amplifier Discussion / Re: Peavy Rage 158 no sound after 1-5 mins
« on: June 16, 2019, 04:29:48 PM »
Schematic shows pin3 connected to ground, so no insulation needed for the IC.
Check D10 in circuit with your meter.  Check for any solder bridges at the IC pins.

9
Amplifier Discussion / Re: Fender Acoustasonic Jr. Squeal
« on: June 15, 2019, 01:20:58 PM »
Try again how you did it with the electric guitar plugged in, but set all the guitar controls (and reverb) to zero.  Still squeal?

10
Amplifier Discussion / Re: HELP Marshall 5203 Master Reverb 30
« on: March 10, 2019, 09:32:40 PM »
Yep.  Notice the 5205 schematic still has 25V caps?  Not possible if that were really a 21-0-21 secondary.
This may sound crazy, but some companies label the transformer or schematics with what the rectified DC voltage will be.  (Roland?)
That must be the case with this 5205 schematic.  So a 15-0-15 secondary like Phil mentioned will give a rectified +/-21V which will drop a little bit under full load and give the 12W at 16ohms that the 5205 specs. 

The 5203 is completely designed around a certain voltage supply.  If you change it, even though you put in higher voltage caps, you would need to adjust the dropping resistors R35 & R36 so that the 15V zeners don't burn.  Then you will probably have to increase the size of the heatsink, which was spec'd for 30W output.  Now you can hope that the power transistors can handle the extra current, and that the speaker can handle the extra power.  :D

11
Amplifier Discussion / Re: HELP Marshall 5203 Master Reverb 30
« on: March 09, 2019, 03:39:06 PM »
No don't do that as you will exceed the voltage rating of the main filter caps which you say is 25volts.
Your transformer should have close to 15-0-15ACV which will reap 15 x 1.4 = 21VDC.
That sounds better.  Solving backwards from 30W into 4ohms, rails would be approx.  +/-15.5V fully loaded.

12
Amplifier Discussion / Re: Help with Gallien-Krueger 200GT guitar amp
« on: March 08, 2019, 01:34:19 PM »
Reverb circuits are normally wired with only the pickup side grounded to the Tank Case. (Not always but most often)
I think you are right that something has changed with regard to the tank.
Other possibilities are that the tank was replaced with same type but different jack grounding scheme (5th character of accutronics tank code), or there may have been rubber mounts insulating the reverb tank from the aluminum plate it is mounted on.

Anyway, good to hear smackoj found a workaround and it's all working fine now.

13
Amplifier Discussion / Re: Help with Gallien-Krueger 200GT guitar amp
« on: March 06, 2019, 01:41:30 PM »
All 3 pieces touch metal to metal.
And you have all these contacts made when testing on the bench?
Does the reverb control affect the hum at all?
If all electrical connections remain the same as on the bench, then it is more likely some kind of EMF due to positioning of components or lead dress.

14
Amplifier Discussion / Re: Help with Gallien-Krueger 200GT guitar amp
« on: March 05, 2019, 04:07:46 PM »
Still have no idea how you could have had -30VDC on that pot if Q26 and it's circuit is ok.
Have you tried the amp now to see if it works?

15
Amplifier Discussion / Re: Help with Gallien-Krueger 200GT guitar amp
« on: March 04, 2019, 10:26:44 PM »
That sounds right.  Now on the schematic there is a straight line down from the E of Q26 to the pot.
So if there is -9V at Q26 E, it must be on the pot as well, or there is a missing connection.

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