ppi pc2150 distorted right channel

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Did you check the big resistors tied to the outputs, they like to open up.

after those I would look at the SIP driver card, among other possibilities these come to mind as most prevalent failure wise.
Look for melted or missing components on the ceramic cards...and possibly you might have to carefully reflow all the solders on the SIP card < this works very often to restore the proper operation> Careful though, it does not like solder flux and excessive heat on those SMD solder connections, you can destroy the card if you not careful

And these cards must be hand made to replace, PPI does not support these anymore, and unless you strip another amp you must build replacements ...At least that's what Perry and I do when we need these....
 
ok i will check the resistors first. if those are all ok i will look at the cards, i think the one on the right is discolored where it attaches to the main board, it is dark brown like it may have been overheated. if i do need to rebuild the board, are the parts easy to find? thanks for your help
 
i checked the resistors and they are all ok. the small board is screwed up. the legs on the bottom were loose and not connected to it anymore and a couple surface mount transistors were also not connected.. i could not resolder anything, i cant figure out how you do it. but i did solder some jumper wires to the components and the right channel now works fine. i would like to fix it the right way could you tell me the secret on how to solder these thing back to the porcelin board? thanks
 
The solder pads on some of these boards are not solderable. When you apply heat (nothing else) the solder will draw up taking the pads with it. Other boards are readily solderable and have no problem with pads lifting.

Sometimes, you can scrape the mask off of the trace and make the connection with a small strand of wire.

Can you post a photo of the board?
 
If you see brown colored surfaces where the solder needs to be, your SOL on resoldering those contacts. The surfaces are destroyed and un-solderable under any conditions I have ever seen.

Believe me I have tried in the past, and its a no go situation. Not even flux will make solder adhere to that brown surface.

If, you still have solder left at the contact site, then you must use a tad bit more heat, and some good fine electronics solder. Don't get carried away and over heat whats left as it is easy to finish off the connection this way.
The ceramic SIP card has unique thermal characteristics hence the reason I think it was used for this device. All the devices mounted on these SIP's thermal track one another and this limits DC offset issues due to temperature variations...IMO

Perry and I both build our own replacements on a as need be basis, because Directed / PPI has left all there loyal old school customers hanging on these cards.
 
I had some glue, it was in tape form. You heat it to I forget but 350F or something and it will glue metal together and when it cools I think it will not melt again. Is very thin, I think you could glue copper onto ceramic but it would be a matter of being able to physically do it. I can find a datasheet on it maybe if you think it would be of use. I can get a piece of it. May be this stuff: http://multimedia.3m.com/mws/mediawebserver?66666UuZjcFSLXTt4xTt4xM_EVuQEcuZgVs6EVs6E666666--

You could put it on the copper then hold it on and iron it more or less. It turns dark when cured. Just an idea. It is only 10 mills thick so it does not slop around. We would clamp it together in an oven.
 
Humm,This reminds me of those ceramic terminal strips used in old Tektronix equipment - they required silver solder,regular solder would 'contaminate' the plating,and dissolve it.
Perhaps those cards are similar?

The original boards were actually called hybrids as the resistance was internal to the board, or the resistance was actually the trace itself. I used regular solder on them when I worked on them.
 
Mummm guitar amps, I just did a solid state fender twin...lol :spin:. Easy money lol lol lol..

I try to stay away from the SS stuff. I like the feeling/fearing of knowing that if I slip, with the probe, it'll be time for a new one. But, I do keep my foot in a saline solution in which I have Earthed. :D

Actually, I am looking for a power-xformer for a 75 Fender Super Twin. this was only produced in 75 and 76 and preceded the Super Twin Reverb. I've looked at several different sites and they only have the output impedance-changer guys.

Thanks
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.