No more 60 Hz hum in a PL2000 preamp.

[George S.]

They seem to have done things a little differently for sure. Think it was because the 700 amp was the first product.
Below is a 2000 preamp chassis sitting on a 700 amp chassis. Very similar design construction and dimensions.

 

[Gepetto]

PL did like their shallow cabinets, didn’t they?

saves money...they liked that too.

 

[George S.]

I knew that was coming! "smile"

 

[Gepetto]

O.K., so I now have films in C24 and C44 and everything is good. I really don't understand the issue I was having. Perhaps the blown phono Browndog was the issue or the fact that I didn't have the self shorting phono jacks installed.
Anyhow, #1 is done. Now going to borrow some parts out of the test unit and finish #2.

The way PL should have built it...

 

[George S.]

Making progress on #2.

 

[laatsch55]

Nice work George!~!

 

[George S.]

Put the voltage to #2. 119 VAC line voltage this morning. B+ and B- are both 13.4 VDC with 25 ohm resistors in series with the secondaries and opamps installed. Going with this resistor value, same as I'm now using on #1.

 

[George S.]

Both preamps are finished. It took a lot of work and time, but was worth it. They sound so much better than before.
Stopped and visited my father today. Mentioned I'm going to rebuild a PL5000 tuner next. He gave me a Boonton 102D FM-AM Signal Generator and a HP 5334B Universal Counter along with the manuals. Said they worked last use but it's been several years.
I'm going to need a larger work space.

 

[J!m]

More importantly:

You need a biscuit for that pooch!

 

[laatsch55]

Both preamps are finished. It took a lot of work and time, but was worth it. They sound so much better than before.
Stopped and visited my father today. Mentioned I'm going to rebuild a PL5000 tuner next. He gave me a Boonton 102D FM-AM Signal Generator and a HP 5334B Universal Counter along with the manuals. Said they worked last use but it's been several years.
I'm going to need a larger work space.

Never EVER turn down free test equipment...

 

[Gepetto]

Never EVER turn down free test equipment...

That is rule number 3...

 

[D-500 Flogger]

Mark, post 16, ran the IEC ground to a transformer screw, higher noise. Used simple wire. May experiment with a safety cap in the future. Incidentally, if I pull the RCA cable from the preamps output jack (this is the soundcards input cable)and hold it out like a antenna, I get a huge 60hz spike on the screen. Then, if I short the jack, the spike disappears. This is with the laptop running on battery. The equipment detects a huge amount of 60hz anywhere close to the house.
Tomorrow I'm going to try a different sound card. Been using a Asus U7 MK2 USB card. Going to try a Focusrite Scarlett 2i4 USB sound interface.
Have to wonder how the labs keep test signals clean from external factors like 60hz. House was built in 77 with all copper wiring, breakers, ground fault in breaker box, 3 conductor Romex, good ground rod bonding to soil best I can tell. No electrical issues in the house. Here's a photo of test setup outside View attachment 53707

George, you are my kind of troubleshooter. I don't hesitate to change my test conditions if I think I'm measuring my surrounding environment instead of the circuit in question.

I still have my 2000, which was the first preamp I ever bought. I retired it maybe 25 years ago when I discovered that my Lexicon CP-2 surround sound processor had a much lower noise floor & passed critical listening sessions.

But seeing you fighting the good fight has got me seriously considering unearthing my 2000 from storage and seeing just how good it can be. (This is why I think this forum is such a valuable resource!) Nice job!

 

[D-500 Flogger]

Well Denny did a great soldering job back in 78 or 79. Every trace is intact and tight.
I have yet to find a broken joint or plastic jack on all three PL2000s.
These Hakko vacuum desoldering stations make this easy.
Now the hard part, getting the old flux off. Wife was nice and got me a new bottle of 99% Isopropyl. Making sure everything is turned off before I use it!

That's a great nugget of info on the Hakko desoldering stations. When I was 20 a Radio Shack pencil tip soldering iron & desoldering wick & off to the races. 40+ years later & I have no shame in giving myself every unfair advantage possible. (If you ain't cheating, you ain't trying hard enough. :0)

Thanks for all your documentation - you are my Lewis & Clark on the best path to take -- it's appreciated! Hope I can someday reciprocate...

Cheers -

 

[D-500 Flogger]

Desoldering the jacks on #2. The Hakko doesn't have a big enough tip to go over the jack lug, so I use it around the lug and finish up with desoldering wick. Used to use Radio Shack desoldering braid, but it was junk compared to Superwick from M.G. Chemicals. Works wonderful. A must have.

Yet another invaluable tech tip! Superwick desoldering braid is going on the project shopping list! Thanks again!

 

[George S.]

Just be very gentle with the old PL boards. Keep your soldering to 700 deg F and don't linger and you'll be O.K. Get up to 750 and the trace will delaminate. A properly calibrated iron is essential. I use a Hakko clone thermocouple to check mine. Yeh it's a cheap clone, but uses genuine Hakko sensors.

 

[D-500 Flogger]

Just be very gentle with the old PL boards. Keep your soldering to 700 deg F and don't linger and you'll be O.K. Get up to 750 and the trace will delaminate. A properly calibrated iron is essential. I use a Hakko clone thermocouple to check mine. Yeh it's a cheap clone, but uses genuine Hakko sensors.

Sir Yes Sir - Copy all, will comply! George, my best buddy's father taught me at age 16 how to rebuild carbs & also took me through my first engine build. He gave me countless tips about technique, and in particular how to avoid killing the patient while on the operating table. Funny how Mr. Laramore's tips have served me so well in so many unexpected places since then...

One of my biggest concerns going into the 'twin D500' (+2000 preamp now :0) restore-a-thon is the sheer amount of rust I'm gonna have to bust off of my component-level workmanship. (In both civilian & military careers I started at component-level work, but as the years went by it was increasingly FRU (Field Replaceable Unit - DEC) & LRU (Line Replaceable Unit - F-16)

But with Mr. Laramore's mentorship I went on & did my first solo engine rebuild successfully! And already my confidence in restoring my 2000 to something I would want to listen to is much higher now that I've spent the evening reading this entire thread from the beginning. THANKS AGAIN for your generosity with the tips!!!

dave

 

[e30m3mon]

Sir Yes Sir - Copy all, will comply! George, my best buddy's father taught me at age 16 how to rebuild carbs & also took me through my first engine build. He gave me countless tips about technique, and in particular how to avoid killing the patient while on the operating table. Funny how Mr. Laramore's tips have served me so well in so many unexpected places since then...

But with Mr. Laramore's mentorship I went on & did my first solo engine rebuild successfully! And already my confidence in restoring my 2000 to something I would want to listen to is much higher now that I've spent the evening reading this entire thread from the beginning. THANKS AGAIN for your generosity with the tips!!!

dave

Funny that you mention your childhood and the mentorship Mr Laramore extended to you. I was fortunate (one might say "damned!") to have grown up in a small neighborhood where I had several "Mr Laramores" but each with a different specialty: mechanic, TV/audio repair man, carpenter, welder and a machinist. Now I spend my time in the Man Cave turning wrenches and tweaking electrons in retirement. I've offered my two son in laws and a few kids in the neighborhood some mentoring, but all seem too occupied in disposable electronics and video games. Oh well....we out here seem to be the last of a dying breed of guys breathing new life into vintage hardware.

It's good to be out here with y'all!

@George S. Did you ever get around to creating that PDF or a final shopping list of parts you came up with during the 2000-II project? I noticed my right channel has dropped a few DBs and when I turn the balance control full right, there is an unusual buzzing sound coming from the left channel. Going to order some parts before pulling out the Weller "scalpel". Will replace the back row of RCAs with through-hole type whie I have it apart this time.
Thanks again
Al

 

[J!m]

E30 M3

Approved.

 

[George S.]

] Did you ever get around to creating that PDF or a final shopping list of parts you came up with during the 2000-II project? I noticed my right channel has dropped a few DBs and when I turn the balance control full right, there is an unusual buzzing sound coming from the left channel. Going to order some parts before pulling out the Weller "scalpel". Will replace the back row of RCAs with through-hole type whie I have it apart this time.
Thanks again
Al[/QUOTE]
Unfortunately, no. Never got to it, but hope to get to it in the future. Need some more testing equipment and earned expertise and experience first. On those PL2000 jacks, notice they are all self grounding. They have 3 solder legs. One hot and two grounds. The inputs use that second ground, but the outputs don't. That second ground on the outputs is a isolated solder pad. I replaced all of mine with NOS jacks and have a thread with the link to supplier.
Here is a link to the best PL2000 service manual scan I've found on the web. It comes from Don Watts Abundant and is hosted on the AudioKarma site.
http://akdatabase.com/AKview/displayimage.php?album=94&pos=1

 

[Gepetto]

] Did you ever get around to creating that PDF or a final shopping list of parts you came up with during the 2000-II project? I noticed my right channel has dropped a few DBs and when I turn the balance control full right, there is an unusual buzzing sound coming from the left channel. Going to order some parts before pulling out the Weller "scalpel". Will replace the back row of RCAs with through-hole type whie I have it apart this time.
Thanks again
Al

Unfortunately, no. Never got to it, but hope to get to it in the future. Need some more testing equipment and earned expertise and experience first. On those PL2000 jacks, notice they are all self grounding. They have 3 solder legs. One hot and two grounds. The inputs use that second ground, but the outputs don't. That second ground on the outputs is a isolated solder pad. I replaced all of mine with NOS jacks and have a thread with the link to supplier.
Here is a link to the best PL2000 service manual scan I've found on the web. It comes from Don Watts Abundant and is hosted on the AudioKarma site.
http://akdatabase.com/AKview/displayimage.php?album=94&pos=1[/QUOTE]

Time = Enemy