PL-700 OTW

VSAT88

VSAT88

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oldphaser said:
The original 700's already have 4uF 150V bypass capacitors installed. (They were made by Mallory and were either brown or orange in color). They are located on the terminal strip between the positive and negative output stages. I don't recall Dean ever removing the 4uF caps and replacing them with .33uF film bypass caps or adding .33uF's to the 4uF caps to an original 700 series 1 amplifier in an effort to remove any oscillations after I installed newer faster output transistors like the MJ15024's, MJ21194's or MJ21196's. At that time, little else could be done to the series 1's other than to add (up to) 33pF "slow-down" capacitors.

SIDE NOTE: If my memory serves me correct........The addition of "slow-down" capacitors will more than likely also reduce the original bandwidth of the amplifier. Particularly in series 1 amplifiers. As an example, lets say a 700 series 1 had a bandwidth around 27KHz and 33pF "slow-down" capacitors are installed. The bandwidth will be reduced very close to 20KHz. Using any value greater will typically reduce the bandwidth below 20KHz. This is all with respect also to the amplifier being driven to rated output into a 8 ohm load and meeting the .25% T.H.D. specification.


Ed
Click to expand...
I will look it over and see what is there. Thanks. Will try to digest the info above as well. Just back from Wal Mart...Arrrrrrrgggg.
 
VSAT88

VSAT88

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oldphaser said:
Jim,

Did you get my e-mail with links to the "Octopus" articles and schematics?
If so, did you decide yet whether to build it or not?

Ed
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I did Ed. Just have not had time to check it out and yes I am going to build one. I have heard of them (octopus testers) for years but never really understood them. Thank you for sending me the info. I will post back when I can about my results. I will most definitely have questions. I have pretty nice signal generator and a 30mhz dual trace scope but no distortion analyzer. The only way I have ever checked transistors were with my simpson 467 meter in diode check mode.
 
VSAT88

VSAT88

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Looks as if it is not the bias transistor that is giving the trouble. New one installed and the amp does the same thing. R channel bias will adj. no problem .300mv-.400mv. left channel will go to .182 and I can get no more. DC offset will 0 out on both channels. Checking surrounding components.
 
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WOPL Sniffer

WOPL Sniffer

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Now I'm a body man too. Seems the customer didn't like somebody's social security number engraved into the Transformer cover so I had to get out the bondo...... In the 70's when we lived in the barracks, they made up engrave our SSN into our gear so nobody could steal it....

Gonna try a trick for blending in the paint to look like the spatter paint from the factory.... If it don't work, I got 3 cans of paint to huff.....


IMG_4505.jpg
 
VSAT88

VSAT88

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I will do the body work you tell me what to check next on Kabooom here, deal ? Stealing gear, not socials, those were the days.
 
WOPL Sniffer

WOPL Sniffer

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Shit, that's an old 1st gen 700.... I don't think I have even looked at a schematic for one. Use your meter and check all the diodes and transistors. Yer not blowing any fuses right? Checked the rail voltages and the farnigulator?
 
WOPL Sniffer

WOPL Sniffer

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Also check Q7, D3/4... I've seen q7 cause that issue or something down there in that circuit. Look at the schematic, there are voltage measurements on the schematic. Slow and steady. And, don't slip.... KABOOOOOOM
 
VSAT88

VSAT88

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On the farngulator, I will check it next, I have keep a can of compression close by just in case I need re pressurize it. Rail voltage directly off the main filter caps/ -106 VAC + 106 VAC/ No fuses have ever blown. I will continue checking all the other parts/transistors/diodes. Good luck finding a legible schematic. I cant find one anywhere that I can read..
 
WOPL Sniffer

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#77
VSAT88 said:
On the farngulator, I will check it next, I have keep a can of compression close by just in case I need re pressurize it. Rail voltage directly off the main filter caps/ -106 VAC + 106 VAC/ No fuses have ever blown. I will continue checking all the other parts/transistors/diodes. Good luck finding a legible schematic. I cant find one anywhere that I can read..
Click to expand...
I got a nice one. I'll go scan it and send it to you. PM me your email
 
oldphaser

oldphaser

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Phase Linear 700 series 1 amps built from January 1971 until approximately July 1973 all used a PL0171 pc board.

I have (2) very rare 700's made in 1970 with two different pc boards which came out before the PL0171's did.

Ed
 
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