Sherbourn 2-100A Amplifier

[edbog]

Would anyone have a schematic of the innards for this amplifier? Trying to repair one-thanks.

[edbog]

Re: Sherbourn 2-100A Amplifier

Since posting the above message, I have taken the amplifier apart and have the main board by itself but I don't know how to attach a picture of it so when I ask a question I can refer to it. Would much appreciate directions because there is a lot I don't know. The pictures are now on the desktop.

[stj]

Re: Sherbourn 2-100A Amplifier

click on "post reply"

type your message.

scroll down to "manage attachements" and click on it.
then choose the files and click "upload"

[edbog]

Re: Sherbourn 2-100A Amplifier

stj:

I followed your instructions. The file(1.31 MB) is in Current Attachments but nothing happens after that. I thought the picture would come up on the message but nothing. If I click on the title of the attachment, I can transfer it as an URL to the message. I want to show the actual picture. The only other thing I can do with the file that's in Current Attachments is Remove it. There is no Upload from the Current Attachments. So that's where I am now.

[edbog]

Re: Sherbourn 2-100A Amplifier

Oops, there it is. But now, how would I have it in the right position?

Thank you for your help.

[budm]

Re: Sherbourn 2-100A Amplifier

Can you read the P/N of those components that are attached to the heatsinks?
What is it not doing any way?
Also should take straight shot pictures of the top and bottom sides of the board.

[edbog]

Re: Sherbourn 2-100A Amplifier

budm:I think my turning the amp. on and off a number of times while using it when I was repairing the two AR 2ax speakers that I have may have caused this problem. The amp. stopped working. The on light wouldn't come on and it blew fuses. Sent it to company that bought out Sherbourn and this seems to be the problem: The output drive IC and both output transistors have blown plus the power switch has to be rebuilt. So I decided to fix it myself but I need lots of help because I can't do it myself and all help would be greatly appreciated to get this novice through it.

budm, I'm not sure but do you want an overheard photo of the card and two sides so you can see the transistors? If not I don't know what you mean by the bottom.

Anyway, I'm sending the overhead now. The front is where the two large caps(6800 mfs)are. Behind them are what I think are relays for each channel.
Starting from front to back there are three pairs of transistors. The first pair, the ones closest to the large caps are: MOSPEC 2SB817E, HO7B the second pair are: MOSPEC 2SD1047E, HD6B, the last pair, the ones closest to the back are:TDA7296 388 D20230. This pair has 8/7 terminals whereas the first two have three. I have researched these and I think I have substitutes for these pending confirmation and input from the Forum members.
The three prong terminal at the front lower left connect to the secondary of the transformer. With the two large caps you can see some semisoft plastic material in between them. I assume this is to keep the two caps stationary and connected to each other and nothing to do with its' function nor is it seepage.

Here is the top view.

[edbog]

Re: Sherbourn 2-100A Amplifier

I hope this is the top view

[edbog]

Re: Sherbourn 2-100A Amplifier

Another try

[edbog]

Re: Sherbourn 2-100A Amplifier

I forgot to add, the caps all look good, no bulging or leakage. Except for the large two caps, there is a small amount of hard(dry) light brown material around the bottom. I don't know if this is leakage around the bottom or something that helps its' functioning.

[budm]

Re: Sherbourn 2-100A Amplifier

OK, you go the picture of the top side of the board, now we need the bottom side of the board so we can see the traces of the board.
You should also check the resistance between the Collector and the Emitter of those four big transistors (2SB817E, 2SD1047E) to see if they have low resistance.

[edbog]

Re: Sherbourn 2-100A Amplifier

More pictures.

[edbog]

Re: Sherbourn 2-100A Amplifier

Closer look at caps.

[edbog]

Re: Sherbourn 2-100A Amplifier

Closer look

[edbog]

Re: Sherbourn 2-100A Amplifier

Here is the underside.

[edbog]

Re: Sherbourn 2-100A Amplifier

Checked the two large transistors.

From the front the left set: #1 only shows OL and no beeping between C & E;
The same when connecting C & B; But when connect B & E, there is beeping and 0.7 ohms. The same result when testing transistor #2 on left side.

On the right side:
#1 shows 0.4 ohms and beeping when connecting C & E; The same when connecting C & B; The same when connecting B & E. With #2 transistor on right side everything is the same as in #1.

There may be too much information here but it seems the two transistors on the left side are not working. Then, what caused them to fail?
I don't know enough to say the set on the right side is working but if i'm going to change left side might as well change right side.

[budm]

Re: Sherbourn 2-100A Amplifier

Checked the two large transistors.

From the front the left set: #1 only shows OL and no beeping between C & E;
The same when connecting C & B; But when connect B & E, there is beeping and 0.7 ohms. The same result when testing transistor #2 on left side.

On the right side:
#1 shows 0.4 ohms and beeping when connecting C & E; The same when connecting C & B; The same when connecting B & E. With #2 transistor on right side everything is the same as in #1.

There may be too much information here but it seems the two transistors on the left side are not working. Then, what caused them to fail?
I don't know enough to say the set on the right side is working but if i'm going to change left side might as well change right side.

It does look like you do have shorted out output transistors, you should remove them and verify them again off the board.
They may have failed due to overload or shorted load (speaker wiring, speaker, etc.), parts do fail, or just poor circuit design.

[edbog]

Re: Sherbourn 2-100A Amplifier

Thanks will do but have to get one of those solder suckers.

But, what about the two TDAs. Could they have been shorted also?

[budm]

Re: Sherbourn 2-100A Amplifier

"But, what about the two TDAs. Could they have been shorted also?"
Have to download the spec for the TDA to see.

[edbog]

Re: Sherbourn 2-100A Amplifier

Here is one spec sheet.

http://www.datasheets360.com/part/de...FY0XHwodY7EAKw

What do you look for to determine if good or bad?

The output drive IC is also burned out. Where is it on the board? Is it one thing or consists of a number of parts that can be changed? It must be different from the 2SB817 & 2SD1047?