Phase Linear Dual 500 Diagnosis Assistance Requested

[grapplesaw]

4.48 ea at Arrow.com

Joe’s price still worth buying from him

 

[zeppelinofled69]

How many do you need

I would need 2 tp9054 transistors to keep things in line with what is in the amp. I do believe I am going to keep what is currently in the amp and buy some replacements while I get it in order. I will upgrade it once I get it sorted out and running right.

 

[grapplesaw]

Ok
You can pull a pair or two out and still run it at 300 -400 watts, Pink Floyd often ran the 500 s to max missing a pair or two. but make sure you take them out as pairs. Ed has some tested used ones you could buy and I can give you some if he doesn’t.

 

[WOPL Sniffer]

I would need 2 tp9054 transistors to keep things in line with what is in the amp. I do believe I am going to keep what is currently in the amp and buy some replacements while I get it in order. I will upgrade it once I get it sorted out and running right.

Upgrade it AFTER you get it sorted out, up and running? Hmmmmmm

 

[grapplesaw]

I can build you a wiring harness to go full complimentary outputts and setup to run a whiteoak control board. It’ll beat anything out there.

 

[zeppelinofled69]

Upgrade it AFTER you get it sorted out, up and running? Hmmmmmm

Why would I shotgun an amp with a whole bunch of new parts without testing and fixing the problems first? I don't have a bunch of money to throw at this thing and it's already going to be better than anything I own and/or can afford to get into, so I'll take my time with it and replace what needs to be replaced. I don't see replacing every output as a necessity at this point.

 

[WOPL Sniffer]

Tick tick tick tick....

Replacing all the outputs is not shotgunning. Considering they are older than shit and probably would blow up unexpectedly because of that. Stressed out transistors can go at any time and will they current share happily without taking your speakers for a road trip next week? Replacing them one at a time is what the repair center does and is a friggin bandaid at best (and a CHEAP temporary fix) . Recapping 40 year old caps is not shotgunning. They will fail and make a mess of your mess. You consider putting in White Oak back planes shotgunning? Replacing old technology with new, shotgunning? No, shotgunning is replacing parts because of bad troubleshooting practices NOT upgrading your amp. Can't afford it? Cool. Replacing outputs all at once is common practice especially if there is modern outputs available which do a better job and are a better choice. Why would you throw new parts at an amp? You tell me..... can't afford it? Cool. I can't afford New speakers so I shotgunned my amp into the 21st century with a gut job and a White Oak treatment. Want to WOPL up on a payment plan? I've heard it can be done, want to risk life and limb with an old dangerous time bomb of an amp? You can do that too. The tech's and info are here for you either way.

 

[WOPL Sniffer]

Pm me your address, I'll send you a bucket full of transistors I've pulled. $10 for shipping and the transistors are free.
9054's
410's

All different flavors....

 

[zeppelinofled69]

You seem to have made some assumptions about what is going on here...

I never said I was just going to get it going and then run it hard day in and day out as if it were brand new. I simply said I wanted to diagnose and repair the amp before I put new output devices in. Yes they are old, and yeah, they may be worn, but if they work, then It lets me get the amp to a point that when I can afford to replace all of them, I don't have to worry about something in the amp taking those expensive new devices out.

Did you read the whole thread? I already stated I was replacing all of the caps that are testing out of spec... which is virtually every cap in the amp.

I also never responded to the WOPL comment, so I am not sure why you brought that up.

I understand the dangers of running old equipment, but I appreciate your concern and comments on the matter.

 

[WOPL Sniffer]

Yes, I got that. I have sockets and all kinds of stuff... You can have it. It may help you get it ready.

 

[WOPL Sniffer]

I have control boards too but they probably wont work on your amp (they are out of 700B/II's

 

[zeppelinofled69]

Yes, I got that. I have sockets and all kinds of stuff... You can have it. It may help you get it ready.

Thanks a lot. This is an incredibly generous offer. I will PM you so we can chat about the details.

 

[WOPL Sniffer]

cool. I got all kinds of spare stuff from tear downs.

 

[zeppelinofled69]

I got my mouser order and replaced all of the electrolytic caps on the front meter board. The intermittent output issue is now gone, but one of the meters has stopped moving with the input. I swapped the 4558s to the opposite channels and the problem moved with the op-amp, so I have ordered some replacements for those.

Still waiting on a few more parts, but as it sits, the amp is almost there. Then it will be on to building an appropriately sized load box so I can start doing some testing and make sure everything is up to snuff.

 

[grapplesaw]

Check the two signal feed wires the supply signal They run from the output relay to the plug on the board. Often poking around in these 40 year old machine can cause one end to come off it’s connection point.

 

[zeppelinofled69]

I have finally received the new output devices. After putting them in and making sure they were isolated properly from the heat sink, I started it up and all appears to be well with the amp.

Only thing that concerns me is the Bias sits just under the max threshold of .6V with the bias pot turned all the way down.

I have ordered new bias transistors, but I am wondering if this will actually fix the problem? Or is the wall voltage too high causing the circuit to be higher voltage than it should be?

 

[Gepetto]

You should not see much effect from the AC voltage input on bias.

 

[zeppelinofled69]

Thanks Gepetto.

Do you think replacing the transistors in the Bias circuit will bring the level down to a more reasonable range? or should I look at any particular resistors for drift? I have ordered new Q106/206, z101/z201, and q102/q202 for the driver boards, so I have all three if they need to be changed. I just wanted to know if this was even something that would affect the adjustment window, or if I should look elsewhere.

Both channels sit in exactly the same spot at about .56 to .58mV across R133.

 

[Gepetto]

Can you shoot me the snippet of the schematic you are referring to so I can relate to the reference designators you are calling out?

 

[oldphaser]

Here is the schematic from the Dual 500 owner's manual.