I guess this is where one publicly states they are a masochist?

[Rabbit 16v]

Hey all. New here, obviously. Hoping to find help. No, not that kind. More of the electronic kind. I am trying to find some help for a PL400 I have. Recently, it worked fine until it didnt and melted the VC on my Altec 604e. So, when this happens, what does one do? Yup, thats right, you buy another PL400 and a PL700 in unknown state. So, now that I have three units to work on (dont have the recently purchased amps in my possession yet), any thoughts on where I should look on this PL400? I suspect cap or solder joint. I did power it back up with an expendable speaker to see what would happen and it would do ok for a few minutes until it started getting warm, and then off it would go. I dont mind just purchasing stuff and replacing in order to update to newer components anyway, but also am not against just fixing it directly.

Any tips or leads on where I should start? I am not super proficient in electronics repair, but I do have excellent soldering skills and various meters, power supplies, scopes, etc.

 

[Lazarus Short]

Welcome! You have come to the right place, but don't ask me, as I know next to nothing about Phase Linear repair. I'm a forum oddball.

 

[Rabbit 16v]

Welcome! You have come to the right place, but don't ask me, as I know next to nothing about Phase Linear repair. I'm a forum oddball.

Thanks! I have a great list of things I need to get fixed up including some HK tube stuff, Fisher 500c, random Dynaco, etc. Im sure to have something that will annoy everyone with my questions, haha!

 

[J!m]

Welcome!

You need to connect with Gepetto here and get a full White Oak kit. One and done.

The others will be along to help you decide which amp to rebuild, but then unload the other two and enjoy the music.

 

[gene french]

Hey all. New here, obviously. Hoping to find help. No, not that kind. More of the electronic kind. I am trying to find some help for a PL400 I have. Recently, it worked fine until it didnt and melted the VC on my Altec 604e. So, when this happens, what does one do? Yup, thats right, you buy another PL400 and a PL700 in unknown state. So, now that I have three units to work on (dont have the recently purchased amps in my possession yet), any thoughts on where I should look on this PL400? I suspect cap or solder joint. I did power it back up with an expendable speaker to see what would happen and it would do ok for a few minutes until it started getting warm, and then off it would go. I dont mind just purchasing stuff and replacing in order to update to newer components anyway, but also am not against just fixing it directly.

Any tips or leads on where I should start? I am n>ot super proficient in electronics repair, but I do have excellent soldering skills and various meters, power supplies, scopes, etc.

imho...
1. make a dim bulb tester...use it to power up the unit ....so you dont destroy your unit ....i use a 100 watt bulb...here is a how to....

2. order a protection circuit as not to fry speakers...
i would suggest wattsabundant.com...
he sells a nice one...
3. use throw away speakers till done...
4. would probably start looking at the output transistors to start....
5. check 2 5amp agx fuses...
send pics ....

there is lots of very smart guys here...i am not one of them....just trying to help...

or if you just want to upgrade....whiteoakaudio.com offers a nice modern upgrade ....referred to here as a wopl... all new parts except transformer and meters and chassis and rectifier.....he also has power supply cap upgrades ..rectifier upgrade...led meter lighting upgrades....
you are at the right place....best forum on the web...
good luck....

 

[Rabbit 16v]

Welcome!

You need to connect with Gepetto here and get a full White Oak kit. One and done.

The others will be along to help you decide which amp to rebuild, but then unload the other two and enjoy the music.

Thanks. I was in contact with White Oak this week who responded with a list of components. I requested pricing a couple days ago and havent heard back yet. I hesitant to operate a parts cannon, but at the same time, a parts cannon would cover a lot of things that have aged and will likely fail as well as upgrade existing components. At least thats how I am seeing it.

imho...
1. make a dim bulb tester...use it to power up the unit ....so you dont destroy your unit ....i use a 100 watt bulb...here is a how to....

2. order a protection circuit as not to fry speakers...
i would suggest wattsabundant.com...
he sells a nice one...
3. use throw away speakers till done...
4. would probably start looking at the output transistors to start....
5. check 2 5amp agx fuses...
send pics ....

there is lots of very smart guys here...i am not one of them....just trying to help...

or if you just want to upgrade....whiteoakaudio.com offers a nice modern upgrade ....referred to here as a wopl... all new parts except transformer and meters and chassis and rectifier.....he also has power supply cap upgrades ..rectifier upgrade...led meter lighting upgrades....
you are at the right place....best forum on the web...
good luck....

Thanks for the response.

1. I already have a light bulb tester. I also have a Eico 1078 that might work better. But I havent used the Eico yet.

2. I will take a look into that. I was not aware the driver I was dealing with was so valuable and such a masterpiece of equipment until I had to remove it from the cabinet.

3. hope to not need to burn through speakers, haha. I might have a dummy load around here too. Have to look.

4. Do outputs tend to work and then just start failing? I did read something about these tending to send 80vdc rail voltage directly to the speaker conns. This would be consistent with what I observed. I was not able to find anything that really explained the cause of this symptom. During the last test it ran for about 15 minutes at low volume until it started to oscillate. I thought that might be a cap thing, but again, im not super experienced on this.

5. both fuses were inspected and seem to be fine.

I can grab pics in a bit when I clear my bench. Been working on Alpine car radios lately, so its all cluttered since those dont take up too much space by comparison, haha!

thanks for the acronym translation, I did see that in my searchings and wasnt sure what it meant. Im not sure I want to rebuild the entire unit, but I dont want to fix it and have to worry about this happening again.

Thanks again for the help!

 

[Gepetto]

Joe is a very busy guy, but I do eventually get to things...

 

[Rabbit 16v]

Joe is a very busy guy, but I do eventually get to things...

I totally get it. Thanks man.

 

[gene french]

the variac limits voltage ...dim bulb tester limits amps...you must have db tester...or you will keep eating stuff....of course its better to have both...it is mentioned at wattsabundant and white oak docs...

i was advised that if you have any fried outputs....its safest to change all...gepetto calls the remaining functioning outputs on the affected channel .... wounded soldiers...i have done both...and have had secondary failures...as possibly a previously exposed output fails ....

i have both...recapped stock units and wopls...
the stock units are nearly 50 years old...they may run 5 years or 5 minutes...you never know.....
just a fun hobby for me...but i do enjoy the music..
its all about the music!!!

do you have a 4 fin or 8 fin?

 

[Rabbit 16v]

the variac limits voltage ...dim bulb tester limits amps...you must have db tester...or you will keep eating stuff....of course its better to have both...it is mentioned at wattsabundant and white oak docs...

i was advised that if you have any fried outputs....its safest to change all...gepetto calls the remaining functioning outputs on the affected channel .... wounded soldiers...i have done both...and have had secondary failures...as possibly a previously exposed output fails ....

i have both...recapped stock units and wopls...
the stock units are nearly 50 years old...they may run 5 years or 5 minutes...you never know.....
just a fun hobby for me...but i do enjoy the music..
its all about the music!!!

do you have a 4 fin or 8 fin?

Yeah, like I said, i havent used it and im not exactly green, but more of the approaching fall and cold temps sort of green, lol!

It just said min or max on the dial, so I wasnt sure if it limited current. I know the light bulb limits current.

Makes sense on the wounded soldier scenario. Granted, it was less than 7 seconds, but I know how fast solid state stuff gets pissed off. Im thinking just replacing the outputs on that channel due to possible damage since the other channel is fine. Obviously, not calling that a complete repair either as there is something that probably caused the oscillation to start. Unless, maybe you think the outputs could have just done it? Still not putting it back into service though without replacing the caps too.

the one in front of me is an 8 fin. I dont know about the other one or the 700.

 

[gene french]

dont forget the dc protect board....

 

[gene french]

Yeah, like I said, i havent used it and im not exactly green, but more of the approaching fall and cold temps sort of green, lol!

It just said min or max on the dial, so I wasnt sure if it limited current. I know the light bulb limits current.

Makes sense on the wounded soldier scenario. Granted, it was less than 7 seconds, but I know how fast solid state stuff gets pissed off. Im thinking just replacing the outputs on that channel due to possible damage since the other channel is fine. Obviously, not calling that a complete repair either as there is something that probably caused the oscillation to start. Unless, maybe you think the outputs could have just done it? Still not putting it back into service though without replacing the caps too.

if one channel is functioning....you can compare left right channels on control board against each other to trouble shoot....or if the other 400 functions...and had same control board....you can swap parts and check against each other...if you aint careful...you will get in vicious cycle ... and keep changing same parts....until you find the root cause.
got that tee shirt....
guys here be really smart...

 

[Rabbit 16v]

dont forget the dc protect board....

on the list for ensuring my drivers are ok. i wish I had known this was a common failure or I would have at minimum fused the speaker leads.

 

[e30m3mon]

on the list for ensuring my drivers are ok. i wish I had known this was a common failure or I would have at minimum fused the speaker leads.

Fuses are always cheap insurance, even if they’re getting pricier.

Welcome to the best knowledge base on “everything”! There’s a little bit of something out here…and a lot of other things.

 

[MusicSteve]

dont forget the dc protect board....

Gene
After fixing your amps and running w normal conductions.
How many times has the Speaker Position Board saved your speakers?

I do think the dim bulb tester is better since it works automatically.
The Variac is manually operated (Dial) which can be slow and after detecting or seeing smoke or smelling it before turning off Lol

 

[George S.]

I religiously use the Variac, DBT, then DUT(device under test). Many times bringing it up at low voltage I've smoked a resistor with the accompanying glow on the bulb.
Full voltage even with the DBT would have been catastrophic to more components. Probably be doing trace repairs or junking the DUT by just plugging it in.
The freakiest thing is bringing up a 700 WOPL build on the Variac and DBT. The 100 watt incandescent will show a orange filament. Takes nerve and faith in your work.

 

[gene french]

Gene
After fixing your amps and running w normal conductions.
How many times has the Speaker Position Board saved your speakers?
I do think the dim bulb tester is better since it works automatically.
The Variac is manually operated (Dial) which can be slow and after detecting or seeing smoke or smelling it before turning off Lol

well..for sure it saved me a few weeks ago when the original 4 fin (woofer duty) decided to quit working...being in service since march of 2022...
when putting a stock unit back on line after service....its nice to have that security ....
every other serious amp has a protection circuit...phase linear decided they did not need one ..well thats flawed logic...
one bad thing about stock amps..is their age...i have replaced transistors that are beginning to leak...after half a century...a lot of reliability has diminished...the last 8 fin had transistor legs corroded so badly that the legs disintegrated at the slightest touch or movement ...
at least that has been my experience, very limited experience at that ...one doesnt know how many wounded soldiers are in there waiting to ruin your day...and speakers....lol
i know when i power up the wopl...its gonna play music.. joe will advise a dcp board on his machine too...electrical spikes, brown outs, outages, etc take their toll on solid state stuff....
parts these days are better quality than 50 years ago...tolerances are tighter at cheap prices ...technology has improved expotentially....
there is also the problem of aging wire that breaks right above the solder point...and dont forget the lifted traces encountered while working on old and poor quality circuit boards (compared to todays boards)...

 

[gene french]

I religiously use the Variac, DBT, then DUT(device under test). Many times bringing it up at low voltage I've smoked a resistor with the accompanying glow on the bulb.
Full voltage even with the DBT would have been catastrophic to more components. Probably be doing trace repairs or junking the DUT by just plugging it in.
The freakiest thing is bringing up a 700 WOPL build on the Variac and DBT. The 100 watt incandescent will show a orange filament. Takes nerve and faith in your work.

i have found that a short yet sincere prayer raises the odds of success...lol

 

[George S.]

Amen.

 

[MusicSteve]

I religiously use the Variac, DBT, then DUT(device under test). Many times bringing it up at low voltage I've smoked a resistor with the accompanying glow on the bulb.
Full voltage even with the DBT would have been catastrophic to more components. Probably be doing trace repairs or junking the DUT by just plugging it in.
The freakiest thing is bringing up a 700 WOPL build on the Variac and DBT. The 100 watt incandescent will show a orange filament. Takes nerve and faith in your work.

Anybody
What a good producer for using both, back in the day, all we had was Variac only. (never used Both)
(some say you should not use both)

Bulb Watt , does anybody have a chart what size to use and what's the differents? pro and cons
good example a shorted , Preamp , 400 and 700 using what would a 15w compared to a 120w?
and when the Device is good?

Thanks