Author Topic: Help with Peterson Preamp and possibly amplifier  (Read 6089 times)

Offline laberge

  • Fiesta Red
  • **
  • Posts: 46
    • View Profile
Help with Peterson Preamp and possibly amplifier
« on: April 26, 2015, 04:13:14 PM »
Hi Guys,

This is my first post to this forum so I hope I'm not asking anything that's been asked before. I'm trying to see images of some wiring and whatnot but I have no idea what these mods are on my preamp (?). I can have help getting the device back to it's original state, but I wanted to see if there was resources out there where I could find clear pictures of wiring or even what the intention of this mod is. It's a 1973 88 key and I think it's a suitcase but I have no idea to be honest!

I'm very new so hopefully you guys can help me. Everything on the piano is very easy to fix and work on but I'm not much of an electronics guy:


.

My best guess is they built in an amp? I really don't know haha. And advice to proceed with this as well would be much appreciated!

Offline pianotuner steveo

  • MIDI Mark V
  • *****
  • Posts: 3272
  • A keyboard player in love with vintage guitars!!!
    • View Profile
Re: Help with Peterson Preamp and possibly amplifier
« Reply #1 on: April 26, 2015, 05:29:11 PM »
No, it doesn't really look like an amp, it looks like they modified the preamp for some reason.

 However, pictures of the inside should tell for sure what is going on.


1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline laberge

  • Fiesta Red
  • **
  • Posts: 46
    • View Profile
Re: Help with Peterson Preamp and possibly amplifier
« Reply #2 on: April 26, 2015, 06:06:52 PM »
Thanks for that. Here's the pics of  the inside.

I still haven't plugged it in yet.






(totally realized my mailing address was right there!!)

I'm guessing they didn't have the suitcase speaker so a mod was made for a power supply? On the rail there is those two added 1/4in plugs which are connected to an RCA



Still something is missing here. I'm not sure though!

Offline vanceinatlance

  • Mark I
  • ****
  • Posts: 219
    • View Profile
Re: Help with Peterson Preamp and possibly amplifier
« Reply #3 on: April 26, 2015, 07:39:14 PM »
If that black transformer in your picture is going to the preamp, I would say the mod is for that to power it and the two plugs added to the preamp are possibly right and left outs?  I don't see where the rca for the harp is connected. Looks like a couple of power resistors  and the orange capacitor were added for the added power supply. Not sure if that's a voltage regulator I see with them there as well.
Just guessing though. I would definitely have a tech look closely at it.

Offline pianotuner steveo

  • MIDI Mark V
  • *****
  • Posts: 3272
  • A keyboard player in love with vintage guitars!!!
    • View Profile
Re: Help with Peterson Preamp and possibly amplifier
« Reply #4 on: April 27, 2015, 08:27:17 AM »
Yeah, that's not an amp, it is the preamp that was modified, but the soldering looks sloppy. Don't know what exactly is going on in there.

I agree with having a local amp tech look at it.
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline laberge

  • Fiesta Red
  • **
  • Posts: 46
    • View Profile
Re: Help with Peterson Preamp and possibly amplifier
« Reply #5 on: April 27, 2015, 12:34:58 PM »
Thanks guys, I'll either get a tech to look at it or just have my dad look at the original schematic and remove any modifications which have been done to it.

What originally went out of the preamp? It's so weird there's nothing that goes out of it other than the external power supply. Was it just the RCA to harp?

Offline voltergeist

  • Mark II
  • *****
  • Posts: 751
    • View Profile
Re: Help with Peterson Preamp and possibly amplifier
« Reply #6 on: April 27, 2015, 12:56:44 PM »
Thanks guys, I'll either get a tech to look at it or just have my dad look at the original schematic and remove any modifications which have been done to it.

What originally went out of the preamp? It's so weird there's nothing that goes out of it other than the external power supply. Was it just the RCA to harp?

RCA is from the harp (the harp output is an input to the preamp).  The four pin circular connector contains power, ground, audio out L, and audio out R. 

The Vintage Vibe cheek block power supply provides a connection for a wall wart and 1/4" outputs for both L&R.  It's a very good solution for suitcase pianos without a bottom cabinet.
Restored or Overhauled: '65 A-model Sparkletop, '78 Suitcase 73, early-'75 Satellite 88, '81 MkII Stage 73, two '77 Mk1 Stage 73's, '74 Mk1 Stage 73
In Progress: 1 '78 Suitcase (2nd one), '70 KMC - Customized w/ Peterson 4x12, '77 Wurli 270

Offline laberge

  • Fiesta Red
  • **
  • Posts: 46
    • View Profile
Re: Help with Peterson Preamp and possibly amplifier
« Reply #7 on: April 27, 2015, 03:27:23 PM »
Thanks guys, I'll either get a tech to look at it or just have my dad look at the original schematic and remove any modifications which have been done to it.

What originally went out of the preamp? It's so weird there's nothing that goes out of it other than the external power supply. Was it just the RCA to harp?

RCA is from the harp (the harp output is an input to the preamp).  The four pin circular connector contains power, ground, audio out L, and audio out R. 

The Vintage Vibe cheek block power supply provides a connection for a wall wart and 1/4" outputs for both L&R.  It's a very good solution for suitcase pianos without a bottom cabinet.

Thank you for your help. I will look to try to restore my Peterson into original-ish condition and buy the cheek block from VV, I love the way they designed it. For the time being I'll just plug the RCA from the harp into my amp to test sounds and other issues.

Offline drpepper

  • Fiesta Red
  • **
  • Posts: 46
    • View Profile
Re: Help with Peterson Preamp and possibly amplifier
« Reply #8 on: April 27, 2015, 04:50:00 PM »
looks like some interesting work

The orange cap looks to be a filter cap - this will filter out any noise a poor power supply will generate.

Under it I notice some power resistors - I would guess these are to drop the input voltage to the correct voltage, but since I guess you don't know what the mod input voltage was these will be of little help.

The power socket on the front is also the output as there are 4 pins. (ground, +dc, left out and right out)

Changing this back to stock doesn't look too hard as it looks like maybe only mods on the power supply

I have recently taken on a similiar project here -
http://ep-forum.com/smf/index.php?topic=8500.0


Rhodes Suitcase 75
gibson 335

Offline Ben Bove

  • Vendor
  • MIDI Mark V
  • *****
  • Posts: 3279
  • Formerly bjammerz
    • View Profile
    • Retro Rentals Website
Re: Help with Peterson Preamp and possibly amplifier
« Reply #9 on: April 27, 2015, 05:03:22 PM »
There's definitely some non-original stuff going on here.  The normal signal chain is RCA from the harp, into 2 accessory jacks, and then into the peterson preamp.  So where they plugged in the black splitter in this pic, that should connect to your harp.



From your pictures - your piano didn't originally come with accessory jacks, it looks like a 1972-ish.  So, two accessory jacks were added in horizontally on the silver namerail (though it should've been vertically).  In your pics they're red-wired jacks.  The problem on yours is that there is no connection from these jacks into the preamp - the signal literally stops here: from RCA to red-wired jacks, to nowhere.  Originally, the pianos have a connection from the accessory jacks into the right side of the preamp box.  So the hole to the right of that orange "Siemens" component is where the audio signal originally entered the preamp. 

I can't tell exactly what the black cable is that's wired into the preamp, but my guess is what people have mentioned - it looks like an attempt was made to power the preamp manually, and they wired up another 2 jacks in the preamp box itself for stereo outputs.  So, the piano could be powered with manual audio outs, and you wouldn't have to bring the speaker cabinet.  As Voltergeist mentioned, the suitcase works by the bottom cabinet powering the preamp and distributing audio through the 4-pin cable.  In order to get around the speaker cabinet, you'd need power and stereo outs and that looks like what's going on here.
Retro Rentals
Vintage Music Gear

http://www.RetroRentals.net
(818) 806-9606
info@retrorentals.net

FB: https://www.facebook.com/retrorentals.net/
IG: @RetroRentalsNet

Offline Student Rhodes

  • Mark I
  • ****
  • Posts: 610
    • View Profile
Re: Help with Peterson Preamp and possibly amplifier
« Reply #10 on: April 28, 2015, 12:01:07 AM »
Is your piano originally a suitcase model?  It may say on the gold foil harp sticker.
Obviously, if it doesn't have leg flanges, it's a suitcase model, in which case you'll need to be very careful with the bottom. 
The bottom on the Suitcase shell are not as thick as found on the Stage model and are easily punctured or broken.

Offline laberge

  • Fiesta Red
  • **
  • Posts: 46
    • View Profile
Re: Help with Peterson Preamp and possibly amplifier
« Reply #11 on: April 28, 2015, 11:17:45 AM »
Is your piano originally a suitcase model?  It may say on the gold foil harp sticker.
Obviously, if it doesn't have leg flanges, it's a suitcase model, in which case you'll need to be very careful with the bottom. 
The bottom on the Suitcase shell are not as thick as found on the Stage model and are easily punctured or broken.

Yeah it's likely suitcase model, nothing written on the gold stamp though (no leg mounts) but the base looks to be of solid wood (see picture). First things first is getting the innards sorted out, the preamp restored and then replacing all the tolex and hinges and whatnot (might not be the best order but its easy to take apart)

See this picture:


Thanks for linking to your rebuild thread drpepper. I'll look into maybe doing something like that with my rhodes -but I might just go with the VV cheek block piece.

I really want to thank everyone for helping me out on this. Restoring a rhodes isn't something I had expected to do but when this one came up at the price ($400 CAD) I just knew it had to be done. Always wanted a rhodes but know I know (almost) everything about it!

Offline laberge

  • Fiesta Red
  • **
  • Posts: 46
    • View Profile
Re: Help with Peterson Preamp and possibly amplifier
« Reply #12 on: April 29, 2015, 11:31:41 AM »
Ok guys, one more piece to the puzzle!!

I was looking at my harp this morning before work and found this extra wire coming from the harp. I'm willing to bet it goes somewhere (hahaha), I didn't have time to check the preamp to see if it was soldered there or if it's supposed to go somewhere else but either way whoever did the soldering on this thing must have been completely drunk... The worst I've ever seen and I'm not very good at it! (ps the red wire is unsoldered)




I'll be sure to update everyone once I figure this out. In other news, I've been slowly removing and cleaning everything out side of the harp, cleaning and straightening the individual dampers (removing the original glue they applied is a lot of work), cleaning hammers and prepping it all for fresh everything - damper felts, new hammer tips and  thats not even touching the frame or the harp!

Offline Ben Bove

  • Vendor
  • MIDI Mark V
  • *****
  • Posts: 3279
  • Formerly bjammerz
    • View Profile
    • Retro Rentals Website
Re: Help with Peterson Preamp and possibly amplifier
« Reply #13 on: April 29, 2015, 12:17:12 PM »
It looks like an additional ground wire, which many people add on if it's missing.

This would belong attached to one of the screws on the sustain rail (that pivots when you hit the pedal).  It helps to reduce a bit of buzz.
Retro Rentals
Vintage Music Gear

http://www.RetroRentals.net
(818) 806-9606
info@retrorentals.net

FB: https://www.facebook.com/retrorentals.net/
IG: @RetroRentalsNet

Offline laberge

  • Fiesta Red
  • **
  • Posts: 46
    • View Profile
Re: Help with Peterson Preamp and possibly amplifier
« Reply #14 on: April 29, 2015, 05:59:10 PM »
It looks like an additional ground wire, which many people add on if it's missing.

This would belong attached to one of the screws on the sustain rail (that pivots when you hit the pedal).  It helps to reduce a bit of buzz.

Thanks for that! Just as I thought I had a lead on this mysterious preamp. I appreciate everyones help with my project. I'm sure I'll have plenty of questions once I actually get it reassembled too.