PL400-700 BABB Pictures

WOPL Sniffer

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#21
Joe, I have been camped out in my shop and assembling all the goodies you shipped to me. Thanks a bunch. I love the BABB and the snubber board, top notch gizmos there buddy. You continue to amaze me (Although I am entertained by watching bread go moldy soooooo) :)

I spaced it and ran out of bridge rectifiers so I ordered some and in the mean time, I slipped an old one in there just so I could finish some testing and It was weird. I fired up the Dumb Bulb and the light stayed bright so I tore into the amp and I went back to the Back Plane bring up (after I removed the back planes and put a different set in there to verify everything, wiring was spot on. DBT was good. I installed the Control Board, still good. As soon as I hooked up the DCP, bulb stayed bright again. I unhooked the AC wires to the DCP, still bright (the outputs are grounded), unhooked the ground wires from the DBT...... Went dim. I used the DCP out of my system amp and it still stayed bright so the DCP is doing it's thing.... I think the bridge rectifier was AFU (it ohmed out lower than an exact same rectifier in my parts pile. It was only putting out a few volts DC until I unloaded the AC by removing the good DCP's and the voltage sprang back up and the bulb went dim.

These amps got here with the 50 Watt Zoebel resistors exploded, shit melted etc... So maybe the bridge Rectifier was starting to show issues. I haven't seen one go bad but I'm sure they do. I should have looked at the signal with the Oscope but my friend I grew up with showed up with beer........ Game over... I'll test the transformer and put it under a load and see what it does. I noticed the hold down screw for the bulk cap strap had backed down into the cradle, maybe it damaged the transformer wiring????
 

Gepetto

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#23
Joe, I have been camped out in my shop and assembling all the goodies you shipped to me. Thanks a bunch. I love the BABB and the snubber board, top notch gizmos there buddy. You continue to amaze me (Although I am entertained by watching bread go moldy soooooo) :)

I spaced it and ran out of bridge rectifiers so I ordered some and in the mean time, I slipped an old one in there just so I could finish some testing and It was weird. I fired up the Dumb Bulb and the light stayed bright so I tore into the amp and I went back to the Back Plane bring up (after I removed the back planes and put a different set in there to verify everything, wiring was spot on. DBT was good. I installed the Control Board, still good. As soon as I hooked up the DCP, bulb stayed bright again. I unhooked the AC wires to the DCP, still bright (the outputs are grounded), unhooked the ground wires from the DBT...... Went dim. I used the DCP out of my system amp and it still stayed bright so the DCP is doing it's thing.... I think the bridge rectifier was AFU (it ohmed out lower than an exact same rectifier in my parts pile. It was only putting out a few volts DC until I unloaded the AC by removing the good DCP's and the voltage sprang back up and the bulb went dim.

These amps got here with the 50 Watt Zoebel resistors exploded, shit melted etc... So maybe the bridge Rectifier was starting to show issues. I haven't seen one go bad but I'm sure they do. I should have looked at the signal with the Oscope but my friend I grew up with showed up with beer........ Game over... I'll test the transformer and put it under a load and see what it does. I noticed the hold down screw for the bulk cap strap had backed down into the cradle, maybe it damaged the transformer wiring????

Hi Perry, the only reason any Zoebel network in a PL amp should blow up is that the amp was unstable and oscillating ultrasonically. The Zoebel power dissipation with a 20KHz sine wave at full output power of a 700 dumped into it amounts to 2W.

The band clamp screw could have done damage depending on how far into the transformer it went.

Usually on 700s, the screw for the band strap feeds from underside of the die cast cradle with the open thread end pointing out of the band clamp.
 

WOPL Sniffer

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#24
Hi Perry, the only reason any Zoebel network in a PL amp should blow up is that the amp was unstable and oscillating ultrasonically. The Zoebel power dissipation with a 20KHz sine wave at full output power of a 700 dumped into it amounts to 2W.

The band clamp screw could have done damage depending on how far into the transformer it went.

Usually on 700s, the screw for the band strap feeds from underside of the die cast cradle with the open thread end pointing out of the band clamp.

I'll figure it out. If the bridge rectifier doesn't straighten it out, I'll put a new transformer assembly in it and tear apart the cradle get all that fixed. . I have 3 or 4 I'm getting ready to install into new homes (WOPL's). I need to get this project behind me soon. I gotta get ahold of Don and see if he will sell me bare boards for the DCP. Then I got 2 Sansui receivers coming in here locally for service. A guy got ahold of me and after we exchanged addresses, turns out he's on the next street over from us.

Me and Sherry are going an vacation. Go ahead, ask where.... Where you say??? We are giving each other Metallica tickets and driving to Los Angeles for our Birthdays and Christmas present. They are playing in LA on the 16th of December. Then we will visit friends (Damn Bikers) and come home.
 

MusicSteve

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#29
Man, that Rectifier is slick....
I bought a bunch of them when Joe first posted them a while back.
Its Amazing how much time it saves and how easy it is to install.
and how Amazing they look.
(working getting it to work w the 700II)

The old way looks easy to do until you try to solder the 4 snubbers
and for me, you end up w a 8 lead mess (not a easy way to bend the leads) Lol
 
Joined
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#31
Sniff, I have had two bad bridge rectifiers in my upgraded PL700B amps. It was the last thing I looked at naturally. Now I replace them all, no questions. They are cheap and then I don't have to worry about them.
Never had any stock bridge go bad , (its been on my worry list)
Did it open up? or short out? what size were they and what size do you use now _)(amps?) They are currently gone up in price.
Thanks Anybody
 
Last edited:

mlucitt

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#36
Never had any stock bridge go bad , (its been on my worry list)
Did it open up? or short out? what size were they and what size do you use now _)(amps?) They are currently gone up in price.
Thanks Anybody
Only one of the diodes opened up, so with three working diodes, the voltage was off and the power out of the main caps was unbalanced causing all sorts of problems. Stock rating for the PL400/700 bridge rectifier is 200V 25A.
I buy the bridge rectifiers 25 at a time from Mouser and the price is only $3.42 each for the 1000V 50Amp version, P/N KBPC5010T. They come 50 to a box if you want a full box, curiously they don't offer a price break at quantity 50.
 

laatsch55

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#37
We have a 36" and a 48" Blanchard surface grinders in the shop. They have magnetic chucks. The 36 wasn't holding the other day. It takes 115 volt DC to run the chuck. After blowing a couple 15 amp glass fuses, literally blowing the glass to pieces. Had to blow a second one cause it was so cool seeing a glass fuse go nuclear.
So after a few minutes we pulled the bridge rectifier and deemed it shorted. Wandler pipes up and says " Great, how long will be down waiting on that?"
I said fuck Wandler I have a drawer full of these at the house. Yep, same bridge as a 700. Had it up and running in 30 min.
I'm a hero..
 

gene french

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#38
We have a 36" and a 48" Blanchard surface grinders in the shop. They have magnetic chucks. The 36 wasn't holding the other day. It takes 115 volt DC to run the chuck. After blowing a couple 15 amp glass fuses, literally blowing the glass to pieces. Had to blow a second one cause it was so cool seeing a glass fuse go nuclear.
So after a few minutes we pulled the bridge rectifier and deemed it shorted. Wandler pipes up and says " Great, how long will be down waiting on that?"
I said fuck Wandler I have a drawer full of these at the house. Yep, same bridge as a 700. Had it up and running in 30 min.
I'm a hero..
you are my hero too!!!
lol
 

Vintage 700b

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#39
We have a 36" and a 48" Blanchard surface grinders in the shop. They have magnetic chucks. The 36 wasn't holding the other day. It takes 115 volt DC to run the chuck. After blowing a couple 15 amp glass fuses, literally blowing the glass to pieces. Had to blow a second one cause it was so cool seeing a glass fuse go nuclear.
So after a few minutes we pulled the bridge rectifier and deemed it shorted. Wandler pipes up and says " Great, how long will be down waiting on that?"
I said fuck Wandler I have a drawer full of these at the house. Yep, same bridge as a 700. Had it up and running in 30 min.
I'm a hero..
Hey Lee,
I've been working with Blanchard rotary grinders and large surface grinders for 45 years. This is rare but I have seen it probably 5 times. Your post really put a smile on my face, very interesting.
Thanks for the post!
Stay warm, colder where you are, but I woke up to -17 without the wind chill this morning :oops:.
 

WOPL Sniffer

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Screw it
#40
We have a 36" and a 48" Blanchard surface grinders in the shop. They have magnetic chucks. The 36 wasn't holding the other day. It takes 115 volt DC to run the chuck. After blowing a couple 15 amp glass fuses, literally blowing the glass to pieces. Had to blow a second one cause it was so cool seeing a glass fuse go nuclear.
So after a few minutes we pulled the bridge rectifier and deemed it shorted. Wandler pipes up and says " Great, how long will be down waiting on that?"
I said fuck Wandler I have a drawer full of these at the house. Yep, same bridge as a 700. Had it up and running in 30 min.
I'm a hero..
Yer OUR hero Lee :)
 
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