New to me PL400

oblivion321

oblivion321

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Mar 2, 2016
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Bingo NY
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Ok. So she's not much of a looker, but I brought her home anyway. Oh... and I have this amp I'm gonna need some help with.;-) Got this thing a few days ago, but you know how life gets in the way sometimes. Bastard. Now I'm free for a minute and wanted to ask some Q's and post some pics. I'm no tech, but the dimbulb on my neck told me I should power this thing up with a DBT and it passed. Checked DC offset. Got -9.4 mv on the right and -3.3 on the left. Seems good to me. Want to check bias, but I'm not sure where R38 is located. Guess that would be my first question. Next I am curious about the outputs. Seems a couple have been changed on the left output and are a different pn than the rest. Is this bad? Last big Q for now. I want to rehab and upgrade this thing all the way, but can only afford to do it a step at a time. What would be a list in order of priority. Obviously check offset and bias and I have the dc protect board I plan on doing tonight or tomorrow. Well, Here she is.....
 

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A couple more pics....
 

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R38 is the 10 ohm resistor on the back wall between the base bus bar and the emitter resistor common tie point.
 
10 ohm----brown black ......the one with the protective sleeve on the lead...
 
Yes, you can gt it close that way, but for final adjustment you have to be off the DBT...
 
Thanks Laatsch55. Didn't get a chance to dig into this any further yet. My daughter couldn't stick the landing and came home from skating with a cracked wrist last night. Maybe today. Any thoughts on the mismatched outputs shown in my pics?
 
The only mixing of outputs that is OK is 909's and DTS-411'S.....because they are the same transistor.
 
These are dts430, so I'm guessing I should go no further until I swap them out. Where is a good source for outputs?
 
Hoping you guys don't get tired of questions. As I stated, I'm not a tech but am looking forward to learning and doing as much as possible myself until I get in way over my head.
 
Ok. So I can order mj21196 from Mouser, but I cant find any RCA410. Anyone know a source? Also, any thoughts or opinions on recapping the board and changing out Q3/Q4 as per the service bulletin? What else should I plan for to get this thing functional in the short term. It's going to be a while before I can go full out rehabbed. Am I sounding like an Idiot yet?:wave: No need to be honest here.
 
The RCA 66456 ARE RCA-410's.......confusing...I know...
 
oblivion321 said:
Ok. So I can order mj21196 from Mouser, but I cant find any RCA410. Anyone know a source? Also, any thoughts or opinions on recapping the board and changing out Q3/Q4 as per the service bulletin? What else should I plan for to get this thing functional in the short term. It's going to be a while before I can go full out rehabbed. Am I sounding like an Idiot yet?:wave: No need to be honest here.
Click to expand...


All very good questions. If Q3,Q4 ARE NOT mpsa93, yeah go ahead. C6 should be changed to a 470uf/25 volts and then search for "Gepetto Mod" to see what to do with the 1N4148 diodes on the backside leads of C6 to prevent latchups....
 
Im having no luck finding any rca-410 by either part number. Would my best route be to swap out the 2 dts430 outputs for some pl909 to match the rest or order the mj-21196 and keep looking for some 410's. I'm guessing the rca 66430 that I have now are not compatible. I just want to figure out what exactly I should order to get me going. I respect your knowledge and this is why I came here. Hopefully I'm not being a thorn for asking stupid questions. I just don't know what the better route is here. Any advice is welome and appreciated.
 
Check that RCA number again, it should be either 66546 or 410,
 
I checked your pics, yeah that's an RCA 66430, never saw one of them...
 
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