No more 60 Hz hum in a PL2000 preamp.
- Thread starter George S.
- Start date
- Joined
- Jan 14, 2011
- Messages
- 74,254
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
Steve had a "Sweet Thunder" mastered version of that----"WOW"....the Sweet Thunder guys were the MFSL bunch who used the MFSL equipment on the weekends and holidays to do their thing. The Sweet Thunder stuff sounded better Steve said because they tried some things the MFSL folks did not want to try and thought it would be a waste of time. When they got caught, MFSL did not want it getting out that it was done on their equipment, and they had to incorporate what they did to any MFSL recording done after that...
- Joined
- Jan 14, 2011
- Messages
- 74,254
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
Board #1 is completed. I'll plug in the opamps after I get the board installed, wired, and voltage checked.
Ran the Quasimodo one more time with the transformer bolted to the chassis to see if any difference. Nope, specifies a 200 ohm in series with a 0.15 uF and a parallel 0.10 uF between each secondary and center tap.
Changed some of theNichicon UFG electrolytics in the phono for a better fit and and UKZ Muse in the power supply.
Should be listening to this one tomorrow while I work on #2.
Ran the Quasimodo one more time with the transformer bolted to the chassis to see if any difference. Nope, specifies a 200 ohm in series with a 0.15 uF and a parallel 0.10 uF between each secondary and center tap.
Changed some of theNichicon UFG electrolytics in the phono for a better fit and and UKZ Muse in the power supply.
Should be listening to this one tomorrow while I work on #2.
Attachments
Done, this is Joe's idea for one and only one ground point between the chassis and board. They originally used two ground points. The screw that goes in that hole will get a nylon washer and won't make electrical contact with the board. The screw by the transformer will be the "star ground".
Attachments
- Joined
- Jan 14, 2011
- Messages
- 74,254
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
#1 is being a BITCH. 119 VAC line voltage. With no opamps installed had 40 VDC between opamps V+ and V-. Installed the original opamps to see if voltage would drop. Dropped to appx 38 VDC. Started adding resistance, 47 ohms on each secondary got each leg down to 15 VDC and change, total appx 31 VDC, so good.
Took it down to test in system just to see if any glaring issues before feeding it a 2 kHz sine wave and checking all functions on scope.
Right channel had low output, so started swapping cables and narrowed it down to the right output jack.
Pulled the jack and the insides were all broken. Crap! Pulled every jack, and 9 of the 18 are trashed.
Lee, now I have learned why you installed different jacks on the DeChristie preamp.
Now to find some replacements!
Took it down to test in system just to see if any glaring issues before feeding it a 2 kHz sine wave and checking all functions on scope.
Right channel had low output, so started swapping cables and narrowed it down to the right output jack.
Pulled the jack and the insides were all broken. Crap! Pulled every jack, and 9 of the 18 are trashed.
Lee, now I have learned why you installed different jacks on the DeChristie preamp.
Now to find some replacements!
Attachments
- Joined
- Jan 14, 2011
- Messages
- 74,254
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
The jacks on my Pl2000 were the reason I retired it, that was 25 years ago, replaced it with a Carver Ct-7. The Carver still sounds great but the memory of the Pl-2000 with the Pl 400 still haunts me. Winter will be coming fast to my neck of the woods so bench time will increase. George keep the pictures coming.
- Joined
- Jan 14, 2011
- Messages
- 74,254
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
- Joined
- Jan 14, 2011
- Messages
- 74,254
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
I don't like the Switchcraft in this application. Look at the photo and you'll see that the traces will loosen from the board just from thermal cycling alone when using solid wire. Braided wire with slack would be the way to go. But disassembly for service or upgrades would be a nightmare with this setup.
As PL designed it, take out the 3 rear screws, desolder the secondaries and line at power switch, and the chassis comes right off. PL had this right, they just needed better jacks.
I'm removing those Switchcraft and looking for new plastic jacks.
I'll use lightweight skinny interconnects or make my own out of Belden 83284 to save stress on the jacks.
I've seen what appears to be NOS jacks on the Bay, VERY high priced, but that may be my only option. I have looked several times in the past for new production jacks, no luck. If anyone knows a source please let me know.
As PL designed it, take out the 3 rear screws, desolder the secondaries and line at power switch, and the chassis comes right off. PL had this right, they just needed better jacks.
I'm removing those Switchcraft and looking for new plastic jacks.
I'll use lightweight skinny interconnects or make my own out of Belden 83284 to save stress on the jacks.
I've seen what appears to be NOS jacks on the Bay, VERY high priced, but that may be my only option. I have looked several times in the past for new production jacks, no luck. If anyone knows a source please let me know.
