Wanted Phase Linear DRS400 (for parts or working)

[Tech19642020]

Hello,

Thank you very much for your reply. Yes I suspect shorted primary windings in one primary as well and the earlier tests performed seem to bear that out. Since it's a dual primary series-parallel I think the windings should be of equal inductance and one measures approximately 80% lower than the other. (while, the checker I have isn't reliable, relative measurements differ dramatically). I used to be able to smell failures like this but I've been a laryngectomee since 2011 and my sense of smell is greatly diminished. However, it's also discolored which may be a further sign of thermal damage to the windings. While the design of this amp certainly has it's limitations and your points are well taken the unit has a certain sentimental value to me that I hope to make it work again. Thanks again for your recommendations and feedback. Take care.

 

[WOPL Sniffer]

Do like Jim wanted to do. Stuff a transistor radio into the chassis and make it LOOK like it really works.

I'm not really a sentimental guy.
If it's junk.......... Strip it and let 10 other amps live because of the good parts. Then you can be sentimental with TEN working amps.

 

[Tech19642020]

Haha, I can certainly understand that rationale and it will be the last resort. Hopefully it won't come to that

 

[wattsabundant]

it's safe to assume that one primary was would and then the second one on top of it. Therefore the second primary has longer wire and will measure higher resistance. I would expect the resistance though to be a few ohms.

 

[WOPL Sniffer]

it's safe to assume that one primary was would and then the second one on top of it. Therefore the second primary has longer wire and will measure higher resistance. I would expect the resistance though to be a few ohms.

HUH?

 

[nakdoc]

It is possible to have shorted windings caused by insulation failure. If you feed 20 volts AC into the good primary and get 20 volts on the "bad' primary, something else is wrong. You can't operate a transformer with any sort of winding short because it changes the mutual inductance.

 

[J!m]

If we know the primary and secondary, wouldn’t it be possible to get an off the shelf torroid to replace the original? Maybe some output voltage tweaking with regulators?

How “unique” is this transformer?

 

[Tech19642020]

Hello,

Found one!
Thank you all very much! I really appreciate all of your input and feedback.

Take care,
David

 

[laatsch55]

How about some pics of the work in progress? We love fix it porn!!

 

[lukievan]

Edit: Just realized I missed the part where you found what you were looking for! Never mind the below unless you still need DRS 900 parts...

I have a DRS 900 that recently started emitting a decidedly un-musical buzzing. I've been trying to source replacement power supply capacitors for it, with no luck. You can see a forum thread about that here.

If in the next couple days I can't find caps with the right values, that fit on the PCB and in the enclosure, I'd be happy to sell it to you. I also have a matching Phase Linear P3800 Preamp if that's of any interest.

 

[mlucitt]

The DRS 900 appeared in 1982, almost 40 years ago. So unless the electrolytic capacitors have been replaced, they have exceeded their design lifespan. You are on the right track...
With regards to the strange markings on your circuit board, the engineers sometime miss the part where the board gets silkscreened and the + and the - get switched around. It is pretty easy to see that the large area in the middle is the ground (-) circuit.

 

[Gepetto]

No need to mark polarity when you use the caps with dummy pins, they only go in one way. That is why they make them that way.

 

[Tech19642020]

Edit: Just realized I missed the part where you found what you were looking for! Never mind the below unless you still need DRS 900 parts...

I have a DRS 900 that recently started emitting a decidedly un-musical buzzing. I've been trying to source replacement power supply capacitors for it, with no luck. You can see a forum thread about that here.

If in the next couple days I can't find caps with the right values, that fit on the PCB and in the enclosure, I'd be happy to sell it to you. I also have a matching Phase Linear P3800 Preamp if that's of any interest.

Hello,

Thank you for your reply, Mouser.com should have the caps you need and should fit without any trouble. ( I replaced the ones in the DRS400) . If you'd like help plese give me the values and I'll check. I did find a DRS400 for parts but would be interested in buying the P3800 Preamp if you do decide to sell it. Thank you again.
Take care!

 

[lukievan]

Hello,

Thank you for your reply, Mouser.com should have the caps you need and should fit without any trouble. ( I replaced the ones in the DRS400) . If you'd like help plese give me the values and I'll check. I did find a DRS400 for parts but would be interested in buying the P3800 Preamp if you do decide to sell it. Thank you again.
Take care!

I changed the caps and it's sounding great again. Pain in the ass to work on...but all's well that ends well!