Menu

Show posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.

Show posts Menu

Messages - Jazz P Bass

#1
I think your meter is trying to average the AC voltage on the two inner pins.
Try with the meter set to to Volts AC.
#2
The rectifier is installed backwards.
#3
It appears to be a power amp issue.
#4
Yes.
Nice work!
#5
Not to beat a dead horse but if the TIP 142/ 147 transistors are plastic enclosed at the collector then you do not need the mica. Just grease.
As a matter of fact, it may hinder the transfer of the heat.
It would be nice if you would indicate what you have as both the BDV & the TIP transistors come both ways.
#6
Short answer: It depends.
 Some transistors have the collector tab totally encapsulated in plastic.
These do not need a mica insulator.
Just heat grease.
 If the collector tab is metal then, yes, it must be isolated from the heatsink IF the circuit calls for it.
 Some amplifier topologies use a grounded collector.
#7
The Newcomer's Forum / Re: Crate GFX212 Volume issue
February 09, 2024, 10:00:04 AM
Run a patch cord from the FX in to FX out.
If the contacts are dirty you will get no sound without a patch cable.
#8
The Newcomer's Forum / Re: Acoustic brand amp blows fuse
February 09, 2024, 09:57:22 AM
I would start with checking the output transistors for a gross short.
#9
Have you tried attempting to isolate the issue.
Do Any controls affect the ticking?
Try using the FX Send to another amplifier.
That is the preamp circuit.
Also, you can plug a guitar into the FX Return which is the power amplifier circuit.
#10
Holy Moly.
What a rat's nest.
All because they didn't use a double-sided board.
I cannot find Any component designators that match that schematic.
#11
Is there an issue with the amplifier?
The resistor in question may be a factory fact.
Please provide a schematic and a pic of the underside of the board.
#12
Not too sure about synths.
 But I did run in to circuits that where designed around the slow slew rate of older 4558 ics.
one in particular was a Tube Works amp that had a 12AX7 blow out that toasted the 4558.
I installed a modern version of the ic & the customer wanted to know what was wrong with the amp.
The distortion was NOT the same.
So, I grabbed the ic from the reverb circuit & swapped them around & wallah. Customer happy!
 Another instance was the original Tube Screamer pedal.
Same thing.
Modern ic is too fast. slew rate wise.
By this time I had accumilated a 'stash' of older 4558s.
Installed one of them. Problem solved.
#13
Are you getting a signal through A112 pin 7 & 1?
#14
Can you supply us with a schematic of your circuit?
https://www.voxac30.org.uk/vox_ac30_circuit_diagrams.html
#15
As long as there is not any dc voltage on the amp connectors, you should be ok.