I have a Wharfdale PM700 pa that has no output through the preamp section. Output works fine. Any chance anyone has a schematic buried somewhere as Wharfdale is unresponsive.
Thanks,
Jason
This?
(http://www.wharfedalepro.com/Portals/0/Images/Products/PM/PM_700_L.jpg)
(http://www.gearslutz.com/board/attachments/low-end-theory/214351d1295024267-yamaha-pm700-direct-outs-pm700-1-2.jpg)
The pros: so many things are brought out that it's fairly easy to localise the problem, as you seem to have worked out.
Con: this style of build is often a real cow to work on - hope you get lucky with the mechanics.
YES!!! that is it.
Do you have this in a pdf form? When I d/l the image the info is too blurry.
Thanks,
Jason
I think that's a Yamaha PM700 schematic.
Although the Wharfedale might be an "unofficial clone" ;)
FWIW:
https://www.gearslutz.com/board/attachments/low-end-theory/214353d1295024267-yamaha-pm700-direct-outs-pm700-newschematic.pdf
I don't think it will be like the Yamaha:
Here it is...
Edit: This is all I could find and now I realize the resolution on it is less than ideal. Perhaps it will help, but hard to read. Sorry.
Okay go to this link and read post #7 in this thread on MEF...
http://music-electronics-forum.com/t35362/
Apparently running that Sumatra PDF reader program allows the values to be read better, if nothing else. I am running linux so I will see how this works running WINE.
Edit: Yup this Sumatra PDF reader does help a tad bit. It is still hard to read but at least you'll have a chance, good luck!
Quote from: J M Fahey on September 10, 2014, 10:20:24 PM
I think that's a Yamaha PM700 schematic.
Although the Wharfedale might be an "unofficial clone" ;)
FWIW:
https://www.gearslutz.com/board/attachments/low-end-theory/214353d1295024267-yamaha-pm700-direct-outs-pm700-newschematic.pdf
:-[ {Why don't they put on bloody TITLE BLOCKS FFS? Shoulda spotted the Yamaha drafting style, obvious now}
That PDF only contains some blow-ups of the input stages, that's all, not the post amps to the right.
I guess
nosaj will just have to resort to a microscope and good old-fashioned tech-nishing then. ;)
Doc, is that the service manual from elektrotanya ?
Quote from: g1 on September 11, 2014, 12:23:51 PM
Doc, is that the service manual from elektrotanya ?
That's the one... For better or for, in this case, worse.
nosaj
Are you still with us?
What is the nature of the problem?
How are you getting on with it?
I now have signal passing through the preamp channels 1-5 now, very low output though ( like putting my ear to the speaker low). Master volume makes no difference when rotated. So I used a pair of headphones and probed the master volume with 1k sine going in ch 5. I get sine on one leg, then move to the other leg of pot hear no sound until I get to like 9 or 10 on switch. part number is 503A 50k pot. Going to sub another in and see how it goes.
jason
That is more likely to be an artifact of using lowish impedance headphones to trace a highish impedance circuit. I'll bet the impedance of your 'phones is a lot lower than the resistance of that pot, and that's how I would expect it to behave, however...
Test it with your multimeter.
Take it out of circuit if needs be.
That may not be the actual problem, so confirm that it's o/c at the top before chasing/replacing parts.
You would be better off using some active computer speakers for this signal tracing.
Ok computer speakers with probe confirm pot is operating correctly. So after master vol it would go to the limiters(clippers)?
If pics would help tell me which ones would be helpful.
Thanks,
Jason
{Finding a readable circuit would be helpful. ::) }
I downloaded the Warfedale PM-700 Users Manual (http://www.wharfedalepro.com/Portals/0/PDF_Data/PM700_Manual.pdf) for a closer look at the front panel.
a) Take a known good lead and plug it into "Main Out" and "Power In" (bottom right on panel) and test.
b) Are you getting normal signals at "Record Out"? "Effects Send"? (With their controls up)
Report results.
Same volume, rec out sounds normal.
Looking at pcb board side it appears a njm4558l was snipped out and there was tone on one of the pins but no others. so being a Operational Amplifiers - Op Amps Dual High Gain. I think I can stop here until I can order one in.
This pa was given to me in an unknown state so anything done to it is unknown.
Will follow up when part comes in.
Thanks,
Jason
Quote from: nosajit appears a njm4558l was snipped out
Ahhh
HA! The old "no op-amp" trick will do it every time. ::)
Just about any pin-compatable dual op-amp will replace that (and most will do a better job, i.e. TL072, LM833, etc.)
Keep us posted with how you get on. :dbtu:
Never having dealt with a sip-8 package. Ill definately have to order some. Wasn't a package I was familar with so it didn't stick out visually.
Thanks for your help ill keep you updated.
Jason
SIP versions are harder to get around here, so I'd be looking at a DIP on a tiny Vero sub-board.
Mouser has them for like.76 cents ea US.
Not "impossible" just
harder because they are generally only stocked by manufacturers' service departments, not by the main component suppliers. DIP? SMD? Sure, but not SIP.
Quote from: nosajMouser has them for like.76 cents ea US.
And it costs $60 to post a small
empty cardboard box from the US to Australia. $60.76 - cheap! :lmao:
Keep us posted on how you get on.
I was going to suggest something similar.
What I do in such cases (Argentina is same as Australia in all the bad ways :( ) is search for a guy , a regular Tech who works at home or in a small shop, not the mighty Yamaha or Roland main service center (who won't even talk to me) who repairs standard Japanese Hi Fi stuff.
Say CD players, VCR, TV, Home Audio in general.
He certainly has found a way to get Japanese parts, including very popular , common as dirt SIP njm4558 , which is used everywhere.
Worst case, one can be cannibalized from a dead junk pile unit.
He won't charge U$0.79 for it, but probably either :"hey, just pick it up and get away from here ;) " or "go to the street corner shop and get a couple beers" .
Or he might ask for similar value, say ... "is $5 right for you?"
Somebody here (Enzo? ... Roly?) once mentioned using a dead Yamaha receiver or something similar for a seemingly inexhaustible supply of Japanese parts.
Must have been Enzo ('tho I'm sure I have a board something like that somewhere in my pile ... but don't we all?). ;)
Thrift shops can be very cheap sources of consumer electronic items to be used for parts.
Update on wharfdale i was able to get another broken one and subbed the preamp from it. It is now working intermittantly.
Sometimes it takes 2 or 3 flips of on/off toggle to turn it on all the way(everytime the psu fans come on) It is a smps I have recapped the power supply as it was loaded with the capxcom counterfit caps. i believe that it is a rail that is failing to come up but not sure how to go about it without a schematic.
Thanks,
nosaj