Wurlitzer 1900 Centennial restoration

[viperz]

Interesting, there is an RCA output on the amp for additional amplifier - "should additional sound distribution be required, model 530 amplifier is provided with an auxiliary amplifier output socket which is not governed by the phonograph volume control but does have the advantage of the automatic level control".
So I should be able to connect this to another amplifier with volume control to see if the first two cascades of the main amplifier are working, right?

[jukenorman]

Hi Eugen,
As well as what you've done, I replace coupling capacitors and anode resistors as a matter of course - coupling capacitors because they are prone to go leaky and anode resistors because I have found that they can go noisy. You could connect another amp at the aux connection if you wanted to do that.
Norman.

[viperz]

Hi Norman, I can and most likely will do that too, but I want to ensure that the circuits are actually working before I start swapping other parts.

I connected an external (solid state) integrated amplifier to the output, and I am getting exactly the same distorted sound at exactly the same low volume level. Which tends to me to believe that the issue I'm experiencing is before the Aux amp output. This would isolate the issue to a couple of vacuum tube circuits before that output. I do understand that I could replace all caps/resistors along with the PCB, etc, but I really do enjoy the troubleshooting process.

[viperz]

Interesting how much the parts have floated on the PCB - both, resistors and capacitors. Looks like some parts have floated far enough for the oscillator circuit to stop working. I rebuilt that circuit quickly - just replaced four paper/wax capacitors and a couple of resistors, and everything is working now. This would be a heck of a job to replace all the parts on that board... I will check with HoneyJukes regarding their new board, but probably cannot afford it anyway.

Norman, when you mentioned anode resistors - you mean the ones connected between anodes and coupling capacitors to the next stage? Most of the resistors on this board are carbon film, and I can see they floated 10-80%... This is bad. 

[jukenorman]

Hi Eugen, I meant the resistors between the anode and the DC supply eg R46, R48 which I have often found to be a source of noise. Some of these old carbon resistors can drift substantially in value. If the PCB is in good condition, you should be OK with it but some of these boards have been badly butchered over the years and the track is very prone to lifting if you are not careful.
Norman.

[viperz]

I checked remaining resistors on the board (resistors under the chassis were checked and replaced as required previously when I was replacing electrolytics), replaced the ones really out of spec. Replaced all film capacitors on the board. Replaced most bumblebee caps... and ran out of parts. Waiting for last 5 capacitors and a resistor (digikey is backed up unfortunately, and I don't have any 1KV rated caps in my stash). Replaced selenium rectifier with modern silicon one. Then will re-test the amp, put it back together, and move onto taking speakers out of the cabinet, checking speakers crossover, cleaning cabinet, replacing all broken glass.
The mechanism is much faster after I oiled the shaft under the spring, but still noisy, especially on first 2-3 cycles... I think silicon rectifier may help a bit with cycle speed, although selenium one seemed to have worked just fine.

[viperz]

Replaced last 5 capacitors and a resistor today. The mech runs much faster with solid state rectifier (or maybe my multiple oil applications to shaft and spring helped) - no noise at all, even on the first cold cycles.

Everything works great (I need to wash coin grinder with alcohol one more time, just in case). Here is a short video with external speaker connected: photos.app.goo.gl/FmSJC7gbnJnQdkz87


Now I am moving onto the cabinet clean-up. There is a person in Texas who is gearing up to manufacture new glass pilasters ($300 USD / pair). I cannot find an affordable top valance (new repro glass is around 350 USD (256 euro). Or just go with all plastic/plexiglass at 90 euro for valance and 90 euro for front pilasters. I am also missing one aluminum pilaster extrusion. 

Also need to straighten the front edge of the center grill piece - have not figured out yet how to remove the grill. It seems to be nailed to the backing?

I also just received contact burnishing tool, will give it a try

[jukenorman]

That sounds like a Wurlitzer! The DC voltage will have increased by replacing the original selenium rectifier with silicon so that alone will gee up the motor! Don't go mad with that contact burnishing tool, there will be many contacts for which it won't be appropriate - that will be covered in the "sticky" on contact cleaning!
Norman.

[viperz]

Thank you, Norman. I only cleaned the contacts behind the button mechanism with that tool. It is the one that Ron recommended in the sticky. It is very very soft. One of the contacts seems to be worn quite a bit and sparks every time in disengages, hence why I got the burnishing tool.

[Ron Rich]

Eugen,
Is that contact "pitted/burned" ? If so, you must use a file to remove the burned portion--then burnish it-- if more than 50% of the silver is gone from that contact pair, the contacts themselves, need to be replaced ! Ron Rich

[viperz]

Hi Ron, I inspected both contacts that I saw sparking- both are very uniform with no visible signs of putting. But uniformly dark. They both function. I'll check tomorrow if they still spark tomorrow.

[viperz]

All 5 speakers connected video: photos.app.goo.gl/nzN2rswZUYDNoAMcA

A couple of contacts behind keyboard still spark occasionally, will have to follow proper cleaning and burnishing on those. Sat idle for a couple of days, then looks like some contact in one of the keyboard plugs lost, then started working again. Will re-clean it all again when I'll be assembling everything into the cabinet.

Ordered several hundred dollars worth of cabinets parts from Netherlands. Will hopefully clean the cabinet over this long weekend, then will be waiting for the cabinet parts to arrive... may give me a chance to check out my 3010, which has been blocked by 1900 cabinet in the garage for this whole time.

[viperz]

Replaced one broken record guide on one of record lift arms.

Also received my digital scale for needle pressure adjustment. Looks like my spring was tightened almost all the way in?? Scale showed 27g... I took it down to 11g, and it is still tracking fine. Just not as much bass I guess. But I have no experience adjusting these vertical tracking tonearms

UPS tracking is showing that all my repro plexiglass from Netherlands is on a vehicle out for delivery. I better start working on fixing the front speaker grill.

[Ron Rich]

Hi Eugen,
If using the Cobra still, I believe they should track at around 7 grams ? Check the service Manual ! Base response-- is the damping material good ? Ron Rich

[viperz]

Hi Ron, I'll dial it down more, manual says 10-12g. Arm moves smoothly, I oiled all the joints previously.
I don't understand why someone would tighten the spring all the way. Wouldn't that mean someone did that to compensate for worn needle?