Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Solid State => Topic started by: plexi50 on May 26, 2010, 01:52:46 pm
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I have a delema here: I have a bad transistor i have pulled from the board. No markings or numbers. How am i going to figure this one out? There is no schematic available and this amp was made in Greece from a small company over there. Any info on this amp is pretty much non exhistant. No schematic either. Is there a way i can figure out what these are and there values from the PT's voltage?
This is in the power section feeding all the 8 power transistors on the back of the amp
(http://i356.photobucket.com/albums/oo5/plexijtm45/Board.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/TOTransistors.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/KM201SolitairePanel.jpg)
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Is it a bipolar supply? I'm guessing probably yes. First determine what the DC rails are. The positive rail should feed a NPN transistor and the negative rail should feed a complementary PNP device. Now you already know they're driver transistors driving the output devices. Are there any part numbers on the output
tubes I mean... devices? That's a starting point. If you can finger out what the outputs are, then you can make a best guess as to what is needed to drive them and then select a device that fits the description.
More bad news. Most of these 1970's transistors are harder to find than NOS 7199's. If there are no markings on the drivers or outputs...... then wow.
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Just guessing, if there are two of those TO-220 transistors then one could be PNP and the other NPN. Or both NPN. I would assume they are not Darlington, just regular power transistors. Are there any numbers on those other transistors that have the heat sinks? They look like the drivers. As mentioned before, is the power supply split +/- or not?
Can you get any resistance measurements from the transistors? This will tell NPN or PNP.
In any case the TO-220 transistors that I use for replacing nearly everything are MJE15032 and MJE15033.
We will likely get moved to the solid-state forum....
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These are driving (3) NPN MJ15003G & (3) PNP MJ15004G power transistors. I need to dig in to supply a little more for more info for you:
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Figure the supply rails and the power output; driver specs can be estimated.
However if the drivers are failed you probably have a cascade of failed parts.
So get the supply voltage and see if one of the Big Chip amps can replace the whole power section. Neater and much more reliable.
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I have not had good results with 140V transistors. If the output transistors are blown I would use MJ21193 and MJ21194. There may be other bad parts too such as resistors, diodes, the biasing string, etc. And be sure to replace ALL of the old electrolytic capacitors.
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http://www.ampslab.com/
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Thats what i am affraid of. Spending an eternity in this amp. All the power transistors are a week old. It was making an irritating distorted sound. Then i went to turn it on one night and one of the diodes smoked up near the TO chip.
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I have some old Peavey power amps that I have been working on for a long time. Just about every semiconductor is blown.
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It's going to be a long month /
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Power output is 200 watts RMS. Power supply rail is 35 VDC. I ran into a bad silicon diode on one side of the TO. But thats not all. I have other parts that are overheating in the chain. I have a dead short here some where. Many round 3 leg transistor cans to remove and isolate. Did i mention i have little SS repair skills?
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That's the way it goes. Now it's July and I still have a pair of Crowns and a pair of Peavey, all large power amps, all with a short SOMEPLACE.
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Well it's been over a year + and i have sorted out all the other issues with this amp. I got the voltages from another working Solitaire this week. All i need is these (2) transistors and im good to go. What would driver transistors be listed under in a parts house?
The power supply rail is 52-53VDC
The pics represent the working amp but is identical to the one i amp repairing
As was stated at the top of this thread the builder in Greece wiped all the part numbers off the transistors in his amps
Corrected: This amp is similar using a different layout
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> The power supply rail is 52-53VDC
There seems to be TWO rails. Is it +/-26V or +/-52V?
I would strongly suggest pulling the entire power-amp and replacing with something fresh, modern, short-protected. The AmpsLab (http://www.ampslab.com/) are suitable. The Bi120 would be suitable for +/-52V supply. Not cheap, but less torn-hair than trouble-shooting a domino-effect failure with little SS repair skills. (I have skills, and might consider the job, but with shipping it would add-up to the price of a Bi120.)
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PRR there are (2) rails and each have 52VDC on them. The problem with replacing the entire power board is this amp is worth a small fortune even in it's not working shape and i want to keep it original as possable. I have checked all parts out on the board and they all are good. The reason the chips blew is someone we know installed a pair of rectifier diodes backwards with the anodes facing each other
This amp is the very first Solitaire KM-201 and not the later built ones. The Greek Bouzuki players will pay close to the cost of a 1964 Deluxe reverb for this particular amp. Have you ever heard one of these? Amazing
If i can not find drivers for it then i may have to call upon your expertise. I have not found drivers so far that exceed 32 VDC input
This is the amp that needs the repair
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That Bi120 does look nice and would be more stable. It's killing me to be so close and yet so far away from this working as it was built :cussing:
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Apologies: this is a more sophisticated amp than first appeared. It has some short/SOA-protection.
You have not indicated which transistor you think is blown.
The voltages on the one TO-220 look reasonable. The other... "identical" is unlikely, they should at least be opposite polarity. Need to mind your + and - in this work.
I don't see a full picture of the power amp board.
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Yes you are right. One rail is positive and one rail is negative but the voltages are the same. Will take pic of full power board after i wake up. Would that mean that one TO-220 would be PNP and one NPN?
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Sort of difficult to get real good close up pics of the power board. Here is what i have. The 330 Ohm burnt resistor still reads 330 ohm but i have changed it out for a new one
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Thanks. My brother came up for a visit; I won't look at this for a bit.
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Roger PRR. Im in no rush. Thanks for your input
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I am going to order these transistors tommorrow and see where it gets me
http://www.newark.com/jsp/search/productdetail.jsp?sku=45J1497 (http://www.newark.com/jsp/search/productdetail.jsp?sku=45J1497)
http://www.newark.com/on-semiconductor/mje15033g/bipolar-transistor-pnp-250v-to/dp/45J1498?Ntt=MJE15033G (http://www.newark.com/on-semiconductor/mje15033g/bipolar-transistor-pnp-250v-to/dp/45J1498?Ntt=MJE15033G)
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I got the NPN & PNP transistors and put them in on thier heatsinks and soldered to board. Powered up and ZERO voltage is coming from the outer leads on each transistor. But my breaker fuse did not trip. Amp stays on but no bias i believe. Id say i should have this working in another year or two. :laugh:
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:sad2: :sad2: :sad2: :sad2: :sad2: :sad2: :sad2: :sad2: :sad2:
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Well i am making some progress in deciphering the TO-39 switching transistors. I have replaced all of them but the one i have yet to verify. I believe the drivers are wrong. I have learned more in the last 24 hours than i have in the past 2 years. I removed and rechecked all the new power transistors on the back of the amp i put in a year ago. Im feeling good with a better understanding of this amps power board
I had to use a jewlers lens to make out the badly faded part numbers on the TO-39 cans.
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Well finally after 2 years i had someone send me the name and phone number of the Solitaire amp builder in Greece. I think it is his son. I got up at 4:00 am to call them and my dam phone wouldnt make an International call. It was 10:00 am there. So i have to try again tommorrow. There is a 7 hour difference in time between the US east coast and Greece. If i can send them the power board to go through and repair to original greek specs i will be tickled pink
Though i feel like i am so close in getting it up and running. I have installed all new TO-39 switching transitors and diodes. All the resistors are good in thier values. There are (3) jfet looking transistors that have no numbers on them at all. They are dead as far as testing them on my DVM goes
So close/////////// :sad2:
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I got a parts list for this amp sent to me from Greece and ordered what i needed last week
I have all the right transistors installed. I am confused on the TO-3 supply wiring
The power supply rails are connected to the (collector)
There are two rails at + & - 52VDC. (3) NPN MJ15003G & (3) PNP MJ15004G / They are isolated from the heatsink and screws
I was thinking they should be connected to the Base. The amp was wired this way when i got it but i have been having doubts about the wiring
I am getting no return voltage from the TO-3 transistors to power up the blue square area of the board
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I got a parts list for this amp sent to me from Greece and ordered what i needed last week
Did you get a schematic from them too?
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I got a parts list for this amp sent to me from Greece and ordered what i needed last week
Did you get a schematic from them too?
No they wont give that up. Im working on it though through a friend of a worker there. If i didnt know better it is some kinda top secret build and im very lucky to have gotten the parts list. I have not translated all of it yet. It's 2 miles long in Greek of course. This has been one intense training course
Im trying to get them to resend the email info in a PDF format. The email format is almost untranslatable