Wurlitzer 1900 Centennial restoration

[viperz]

Thank you, gentlemen. It ended up being one of the screws that hold the amplifier heat shield in place. I am migrating it to hold the select lamp housing, as it makes much more sense, and looks like someone lost that thumb screw long time ago.

Ron, I will remove the lock completely, I guess, soak it in solvent, and then use proper graphite lube. Thank you.

[viperz]

I keep finding in the cabinet and reading about random wood pieces and insulator pieces inserted between parts of the cabinet. I guess, those are to reduce vibrations of certain parts? I found a small insulator piece, which was supposed to be between top left pilaster casting and big plate that goes under keyboard. Forgot to put it back until it was too late - nothing is rattling in that part, at least not yet... I managed to insert all wooden pieces where they belonged inside the castings. Also someone mentioned there were cardboard pieces in their 1900 between keyboard casting and the metal plate under it. There were none in mine... How concerned should I be?

[Ron Rich]

Hi Eugen,
On the "cardboard" -- was not cardboard on the 1900's, was fish-paper, and it MUST be there on the 1900 model-- don't know about your model--how close is the keyboard to the metal ? Ron Rich

[viperz]

Hi Ron, I definitely added the new small insulated sheet between C-D buttons and the casting, as there was only like a millimeter between those two, as per your advice.

Or are you saying there should be a piece of fish paper under the whole bottom keyboard piece? Just looked there - damn, those bottom solder joints are like a couple of millimeters from big metal plate?!

[Ron Rich]

Hi Eugen,
Like I said-- I dono what that section looks like on your model, but on the 1900's, it covers the whole back of the keyboard ?? Ron Rich

[viperz]

Ron, mine literally had nothing. I added a small strip right under the contacts. Should it be much bigger?

photos.app.goo.gl/f8LoUZtgweRjEJnKA

[Ron Rich]

Eugen,
I tolt you -- I don't know what that model had Ron Rich

[viperz]

Ron, you mentioned that on 1900s the fishpaper covered the whole back of keyboard. On my 1900 there are none, not even sign that it was there before... Someone sent me a photo of insulators that they found under their keyboard (in 2000 model): photos.app.goo.gl/8ezKnW1RZ21vrdX8A

Here is their keyboard: photos.app.goo.gl/SvHKvL5vjkhM9R1H6 , mine definitely didn't seem to have that fishpaper underneath. 

I think Wurlitzer must have added those three fishpaper pieces in the later serial numbers based on feedback from the users/distributors, and mine must be an earlier example without that fishpaper. I did add a piece of insulation right under bottom number contacts, so will see how and if it works once the mech will be reinstalled. 

[viperz]

So today was supposed to be a big day - I got some help to put the mech back in the cabinet. Right off the bat I got two problems.

1) Coin registered, letter-number selection would register and cancel, but nothing after that. I could manually trigger the selector pins of course. I opened everything up, cleaned every contact in every relay, then noticed timing relay 2 not picking. 0.4A slow-blow fuse on the coil was ruptured. Replaced the fuse, everything is working now. Why would that fuse blow? It has been working for weeks outside of the cabinet..

2) Now tackling issue #2. Previously, all pieces were interconnected but sitting on isolating boxes. Now everything is together. So now the amp input is picking up noise badly somewhere at the input of course. It is volume dependent, so it is not a 60Hz ground loop. Will have to figure out where in the world it is catching that noise and how to eliminate it. It is quite noticeable obviously when I select empty record slot and mute circuit disengages.


Also put an order through Stamann in Germany for the missing pilaster inner extrusion, some rubber channels and new green Cobra cartridge... Hopefully that's the last big expense. Apparently Stamann may take weeks to even process the order according to their website, but they're the only ones who carry the extrusions, and their cartridge price is lower than from their US counterparts ($120-130USD vs 65 euros). 

Also ordered new 12AU7 Gold Lion low-noise tube. Want to see how much improvement that tube may offer in the oscillator stage. 

[jukenorman]

Hi Eugen,
Is the hum still present when you pull the phono input plug from the amplifier? I would be guessing that it is ground related and if the problem is around the input, I cannot see why it wouldn't be volume dependent?

Norman.

[Ron Rich]

Hi Eugen,
Try "flipping" the line cord over-- does that stop the hum ?? Also look at the B+ area-- any jacks used there ? Wiggle the plugs around and see if the hum changes volume---
Ron Rich

[viperz]

Hi gents, I think if it was ground related, the hum would be the same independent of volume. I'll definitely try flipping the line plug, and maybe even try an isolating transformer. From what I see so far, the front tube is picking up noise in the cabinet - if I touch it with my finger, the noise increases. It obviously did not do this outside the cabinet where there was much more space around the amp. That cardboard heatshield around the amp would benefit highly if it had metal foil on it connected to ground, or even if front couple of tubes had metal tube shields on them. I will also try unplugging the input, but I tried rerouting the cable while powered, or bring my finger towards the needle as close as possible, and the noise floor did not change.

[Ron Rich]

Hi Eugen,
Is that tube "shock mounted" on that amp-- didja try changing that tube ? Ron Rich

[viperz]

Hi Ron, yes, that's the one. I just ordered the new one. Stupidly enough, I don't have any spare new 12AU7 tubes in the house.

[Ron Rich]

OK-- Is the shock mounting still good ?? I have seen them "stiffin up" enough that they transmit mechanical action, to the tube ! Ron Rich