PL400 II Resurrection

mlucitt said:
That is a lot of heat transferred to the Control Board. Melted the solder?
Even if we are sending you a "gift" or "samples"? Is there no way around the customs and VAT even if the declared value is 1 Euro? Maybe we can barter for chocolate? 12 transistors for 1 Kg of milk chocolate, fair?
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Nope, that solder is 4% silver. It's a bastard to get to flow and worse to remove.

Assigned customs value iis not related to real, invoice or other verifiable cost. Customs roll the dice and assign what they think the number should be.
I just imported a WHS 300 gauge from Willy Herman. It arrived on July 16th and was released from bpost admin last Friday. It cost around 200 Euro, and there's an 80 Euro surcharge. Not in the least because duties and VAT are calculated upon the total amount, so you're also paying taxes on shipping.

But if you want chocolate I suppose I can send you 10 pounds or so...
 
That board is fried. Some of the plated through holes are destroyed. Board repair (done correctly) is a bitch and then setting new eyelets requires tools. If you plan on cobbling this back together, you would be asking a lot from the helpers on this site and then you may be wasting their time if your "Repairs" of this board is done incorrectly. Pay the Money and do it RIGHT. Import the transistors and get a new board. You'll have nothing but troubles with kludged shit and 40 year old transistors. These guys are much too nice to tell you that your amp is in peril. I'm not. Use the boom box till you can fix it correctly.


TimeBomb.jpg
 
Q9R seems to have survived, measures OK. Q3R, Q4R and Q5, 2 of the 3 are shot, I think Q4R was OK, but didn't take enough notice when removing.

Should I also order replacements for the PL400II bias transistors while I'm in there ? So far the bill is around 100 Euro, including all the power transistors (not the drivers) including everything (shipping too) so I'm OK still...

Pete
 
I don’t own a boombox and trying to repair that board is going to cost me 8 Euro in parts. I’ll take a stab at it if you don’t mind. I’ll let you know how it pans out.
 
TapeHeadOne said:
Q9R seems to have survived, measures OK. Q3R, Q4R and Q5, 2 of the 3 are shot, I think Q4R was OK, but didn't take enough notice when removing.

Should I also order replacements for the PL400II bias transistors while I'm in there ? So far the bill is around 100 Euro, including all the power transistors (not the drivers) including everything (shipping too) so I'm OK still...

Pete
Click to expand...

You may have wounded Q9 which has a base current limit of 1A max. but the limiting effect of the 2 resistors in that chain produce 0.8A in that failure mode so you may have squeaked by.

If you had the WO backplanes in your amp, the 0.5A picofuse would have saved much of that damage you observed.
 
To quote the inimitable Mr. Scott : if my grandmother had wheels she’d be a wagon, sir. I’ll have to play the hand I was dealt ;)
 
It looks like those MJ21196's are also usable as drivers. Haven't found a stand-in for the 2N3403. Mouser has one in stock, and they're backordered. Strange, these thingse are ancient.

Peter
 
Do not use the same number as a driver if used for an output in quasi mode. In full comp mode they have to be the same.
A very good sub for the 3403 is the 2N5088. You will have to transfer the P-strap to the 5088. Pin outs are different.
 
Thanks Laatch. I'm reading now the drivers are just restamped RCA 410's. I think there are no real replacements for those. So It may be going full comp after all. I'll order some extra MJ21196's just to keep my options open.
I may buy another 400II just to keep as original.
 
Yep, good ol 410's. And the old XPL 909'S were rebadged Delco DTS -411's..
410's do come up on ebay quite often.
 
Any electronic supply shops local to you where you can get parts locally?
In the state where I live, electronic supply is limited to light bulbs and extension cords,
so I wouldn’t be a stranger to your frustration.
 
No, they're all dead. Even the ones around the uni where the electric/electronics engineers are trained have all shut up shop. Components aren't a viable business anymore. Luckily ordering from RS, Farnell or Mouser is a singe. I've got the first shipment of stuff incoming. Maybe get it going again with the old board first, take it from there.
 
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The nice people from Houser had a big pile of parts delivered so I can start fixing stuff20190814_161342.jpg

Let's get to it !
 
Why the 4% silver solder??? If 63/37 is good enough for a $50 million dollar fighter jet, it should be fine for the amp.....
 
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