I believe its a 32 amp Pyramid, I think its adjustable up to 30V, Ill have to keep an eye out for a scope, I just might have access to one of those too not counting my chickens yet tho.
What is the DC voltage on pins 9 and 10 of the TL494?
On the emitters of Q05 and Q11?
On the gate legs of the power supply FETs (one from each end of the 3205s - Q09 and Q12).
On the emitters of Q05 and Q11?
On the gate legs of the power supply FETs (one from each end of the 3205s - Q09 and Q12).
Pin 9 and 10 have 4.15-4.25 volts, as well as the 2 legs on each of Q05 and Q11 and the irf3205's
That may be good enough so that you don't need the variable supply for this repair (but it would be good to have if you intend to do more repairs).
Check the solder pads for the rectifiers. Check from the center to the outer legs, do you read a constant short on any of those?
Check the solder pads for the rectifiers. Check from the center to the outer legs, do you read a constant short on any of those?
I bought it went to hook it up and total failure, So its possible it had this problem before the power supply blew.
Do you see any components that appear to have new solder? The original solder connections are very consistent and generally dull.
Ok I went over the board with a magnified lamp and the only thing I found was a possible bad connection on a blue rectangle close to 4 capacitors marked 105K100, I resoldered it, should I put the rectifiers back in and try it or should I wait. My dad mentioned my grandfather had an old scope in the basement would that possibly work? Im not sure how old it may be.
Post a photo of the component that had the bad solder connections.
Old scopes are OK as long as they have a triggered sweep. What make/model is it?
Old scopes are OK as long as they have a triggered sweep. What make/model is it?
The scope I have access to is an old tube type scope so Im not sure it will be what I need. What would the scope allow us to do?
Would this type of scope allow us to do what I need? Ebay item 271252997929, its a Tektronix 475.
Would this type of scope allow us to do what I need? Ebay item 271252997929, its a Tektronix 475.
Post a photo of the front panel of the scope you have after confirming that it works.
That scope would do everything that you'd need for most all repairs. Do a completed item search to see what they sell for. I'd expect it to sell for over $200.
As a side note, that's a TAS475. It's much different than the older 475.
That scope would do everything that you'd need for most all repairs. Do a completed item search to see what they sell for. I'd expect it to sell for over $200.
As a side note, that's a TAS475. It's much different than the older 475.
I doubt that that would be usable.
Reinstall the rectifiers and remove all of the output transistors. After removing the outputs, make sure that there are no solder bridges between any of the pads.
Will it power up without the power supply FETs heating up?
Reinstall the rectifiers and remove all of the output transistors. After removing the outputs, make sure that there are no solder bridges between any of the pads.
Will it power up without the power supply FETs heating up?
Ok I installed the rectifiers and removed the outputs and lo and behold 2 shorted outputs, How did I miss that? Is it because I checked them in circuit? or did I make a rookie mistake?
I lost the bid on the scope, Im still on the hunt, is there anything specific I should be looking in for a scope?
I lost the bid on the scope, Im still on the hunt, is there anything specific I should be looking in for a scope?
Did you check them properly? If you don't discharge the gate/source, they may appear shorted. The following page has a section for testing FETs:
Basic Amplifier Repair - Transistor Test Applet Link
A simple analog scope is all you need. Either post auction numbers or email me directly. The used BK Precision 2120B scopes go for about $150 and at that price, they're a good deal.
Basic Amplifier Repair - Transistor Test Applet Link
A simple analog scope is all you need. Either post auction numbers or email me directly. The used BK Precision 2120B scopes go for about $150 and at that price, they're a good deal.
All three pins of one irf9640 and one irf640 and a dead short. Boards all cleaned up ready to go. Now on to the KX2500 with the same problem.
Ill purchase a scope when payday comes, I plan on repairing more amps, I figure after repairing a few that I should start progressing in the troubleshooting department.
Ill purchase a scope when payday comes, I plan on repairing more amps, I figure after repairing a few that I should start progressing in the troubleshooting department.
- Status
- Not open for further replies.