I have recently acquired a vintage amp (Model TP45) made my Webster Electric. There are not a lot of things that I can find out about it except for what is on the back of it.
i don't know what the line screw things mean and have not used them or that button which seams to be the ground. I have tried to use 1.5 amp slow blow fuses, but they keep getting blown. Any help on getting this thing running would be great. Thanks.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
i don't know what the line screw things mean and have not used them or that button which seams to be the ground. I have tried to use 1.5 amp slow blow fuses, but they keep getting blown. Any help on getting this thing running would be great. Thanks.
Hi DeadSpeaker,
Okay, you have an old mono PA amp.
Fuses blowing instantly means you have a fault in a high power stage. Could be shorted rectifier diodes, main caps or output stage. There may be a combination of faults since a new fuse was put in. It's not unusual to see a blown output stage and shorted rectifier diodes. What may follow is an open transformer primary if you keep sticking fuses in it.
-Chris
Okay, you have an old mono PA amp.
Fuses blowing instantly means you have a fault in a high power stage. Could be shorted rectifier diodes, main caps or output stage. There may be a combination of faults since a new fuse was put in. It's not unusual to see a blown output stage and shorted rectifier diodes. What may follow is an open transformer primary if you keep sticking fuses in it.
-Chris
Hi DeadSpeaker,
That really depends on how much you know and what equipment you have. An experienced tech may be able to repair it properly and set it up without a diagram. A layperson may need to take an electronics course and but test equipment and a manual to get it working.
Where you you fall in that range?
-Chris
That really depends on how much you know and what equipment you have. An experienced tech may be able to repair it properly and set it up without a diagram. A layperson may need to take an electronics course and but test equipment and a manual to get it working.
Where you you fall in that range?
-Chris
Well It is not rocket science to read the values off of capacitors and solder new ones on, but I'm not sure if it is worth it. I'm trying to use it to power a speaker cabinet that has a input value of 65 watts. I know this amp is not enough to meet that requirement, but I wanted to see if it would at least drive the speakers some what. So should I give up my dreams and ditch this thing or what? Thanks for the help.
Hi DeadSpeaker,
I don't know where you got the idea that properly repairing an amplifier is easy. BTW, most techs can not repair an amp properly.
But I did ask, what equipment do you have. That included meter(s), soldering stations (notice it isn't an iron) and anything else. Also, what experience do you have? Is there someone who can help you?
-Chris
It may have enough power to burn those speakers out. Maybe not. It will be loud considering that if you double your power, it's only a 3 dB increase. That's not much.
There is much more to it than you may think. How stupid do you think these good techs are. This may be your first error and I think you may have just insulted all the good techs out there!
I don't know where you got the idea that properly repairing an amplifier is easy. BTW, most techs can not repair an amp properly.But I did ask, what equipment do you have. That included meter(s), soldering stations (notice it isn't an iron) and anything else. Also, what experience do you have? Is there someone who can help you?
I don't know. Are you willing to put any effort into this or not?
-Chris
anatech said:
a mite overbearing -
DeadSpeaker did not ask to become a tech.
find out, if hes got a meter, and walk him through
71
http://www.angelfire.com/vt/audio/tp45.html
I don't have any experiance with this sort of thing at all. The only equipment I have is an ohms meter (Which for whatever reason only responded to about 50% of the resisters and other thingums) and the screw driver that I used to open the thing up. I'm willing to spend a few dollars on this (like $30 US) but I don't want to get far into this if there is not any hope that it will perform. My main goal anyway is to drive those speakers at a level that is adequate for a small venue (used for singing in a rock band at a club)
Hi DeadSpeaker,
This is a really nice amp. It will do what you want. However, it uses tubes, a pair of 6L6's for outputs. This means high voltage so you must be careful. This is worth keeping and fixing up.
Things that come to mind are all those capacitors. Especially the smaller coupling capacitors. This will require patience, but you can do it if you are careful. Step one, take it apart and take a few digital pictures. Pictures of the tp of the chassis, and many good ones of the underside where the wiring and parts are. Two, download and print out the schematic. Download a full resolution one, this attachment is a lower resolution. We will be here for questions.
If you were to buy a good DVM, it would serve you well for many, many years. Buy as good a meter as you can afford. You'll use it for everything. A Fluke is a very good brand.
-Chris
This is a really nice amp. It will do what you want. However, it uses tubes, a pair of 6L6's for outputs. This means high voltage so you must be careful. This is worth keeping and fixing up.
Things that come to mind are all those capacitors. Especially the smaller coupling capacitors. This will require patience, but you can do it if you are careful. Step one, take it apart and take a few digital pictures. Pictures of the tp of the chassis, and many good ones of the underside where the wiring and parts are. Two, download and print out the schematic. Download a full resolution one, this attachment is a lower resolution. We will be here for questions.
If you were to buy a good DVM, it would serve you well for many, many years. Buy as good a meter as you can afford. You'll use it for everything. A Fluke is a very good brand.
-Chris
DeadSpeaker said:
Hi.
The first thing I would do is to open the case and see if there is a foreign body inside which could be causing a short.
(obviously with the amp unplugged!).
Next, after noting where the tubes go, remove them all, replace the fuse and plug in. Does the fuse still blow?
Andy
Well I looked inside the thing pretty well. I don't know if the reason that the meter did not respond to some resistors is because they are blown or if the meter is not powerful enough. What is my next step now that I've seen inside and have a diagram. Also, is there a way to test the tubes? I know I posted this in the solid state section, but that was before I opened it up and realized that there were tubes in it. Thanks for the help everyone.
Edit: Sorry I posted this after you guys put a bunch of messages up. I'll post more picture soon. The Ohms meter says "woods 1304" on it. Should I really power it on without the tubes in it? What will that tell me?
Edit: Sorry I posted this after you guys put a bunch of messages up. I'll post more picture soon. The Ohms meter says "woods 1304" on it. Should I really power it on without the tubes in it? What will that tell me?
Hi DeadSpeaker,
Okay, we are in the right forum now.
You may need a better meter, and also get comfortable with it.
Do not apply power to this until the coupling caps have been replaced. If you don't follow this advice, you may cause enough damage to make this amp not worth fixing.
Smell the transformers. Tell me what they smell like before you start.
-Chris
Okay, we are in the right forum now.
You may need a better meter, and also get comfortable with it.
Do not apply power to this until the coupling caps have been replaced. If you don't follow this advice, you may cause enough damage to make this amp not worth fixing.
Smell the transformers. Tell me what they smell like before you start.
-Chris
The transformers don't smell smoky or bad or anything. I'm glad that i wiped it down before I did that though. Are the coupling capacitors all the yellow ones in the picture? Here are some pics.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Hi DeadSpeaker,
The next job would be to replace the filter capacitors. The brown one with three wires sticking out is one, the others are cans mounted on the chassis.
My feeling is that one or more diodes shorted.
Do not power up this unit until these things are done.
If you want to do a really good job, measure the resistors. Replace the ones that are far away from the marked values. I find that parts like the 220K ohm tend to drift a lot (red-red-yellow-[gold/silver/none]). Others too, but try to measure some of those to get an idea how your meter is working.
-Chris
Yes.
The next job would be to replace the filter capacitors. The brown one with three wires sticking out is one, the others are cans mounted on the chassis.
My feeling is that one or more diodes shorted.
The smell to watch for is a burnt, sweet smell. That's bad! Once you smell it once, you will always remember it. It's not an unpleasant smell, just means bad things happened.
Do not power up this unit until these things are done.
If you want to do a really good job, measure the resistors. Replace the ones that are far away from the marked values. I find that parts like the 220K ohm tend to drift a lot (red-red-yellow-[gold/silver/none]). Others too, but try to measure some of those to get an idea how your meter is working.
-Chris
Alright well the brown filter cap is 100/50 volts, and the one next to the little transformer is 450 volts, and then I think that the can thing next to the big transformer is one too (maybe 10-500 volts from what I can see). From what pictures i've posted, is that all of them?
Where do you recommend I order these parts from? I'm trying to come up with a parts list and an estimated total cost. The meter and the soldering iron I'm going to borrow from a friend but he doesn't know that yet.
How do you know if the tubes and transformers are still good? Is it possible to test them?
Thanks for all the help.
Where do you recommend I order these parts from? I'm trying to come up with a parts list and an estimated total cost. The meter and the soldering iron I'm going to borrow from a friend but he doesn't know that yet.
How do you know if the tubes and transformers are still good? Is it possible to test them?
Thanks for all the help.
I don't mean to rain on your parade, but you may be disappointed with the results.
At some point in time I promised myself I would never waste any more time on a PA amp. It is for pumping midrange through a store speaker system. It may have filters and/or a special output transformer that keeps the lows out of the output. This is to maximize screamablility through a department store, car dealership, etc.
It probably was not intended for high fidelity audio. It also looks corroded: not a good specimen for a beginner. Lots-O-Luck, Mark
At some point in time I promised myself I would never waste any more time on a PA amp. It is for pumping midrange through a store speaker system. It may have filters and/or a special output transformer that keeps the lows out of the output. This is to maximize screamablility through a department store, car dealership, etc.
It probably was not intended for high fidelity audio. It also looks corroded: not a good specimen for a beginner. Lots-O-Luck, Mark
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