Wurlitzer 200a electrolytic capacitators

[fozziemusic]

I found out that my 200a has some seriously wrong voltages on the reed bar (it appears that only one of C30, 31 and 34 is working) - with readings starting about 80 volts and dropping to 52V after measuring for a few seconds - not sure if that is a sort of loading effect of my DMM but I'm nowhere near 150V. Other voltages seem to be ok-is - the +/- 22.5V is 24.5V in my amp, other voltages are spot on or similarly off.

While I'm at it to replace those caps, I would like to change the big cans too, they are still the original ones. I'm not that familiar with electronic parts though - it is clear to me that I should order 2200 uF radial caps, but I'm not sure of the voltage rating (it says 'WV 35' on them - is that 35V?). I would expect higher for power supply caps - but I guess they are after the transformer so maybe that is correct. I'd like to be sure though.
And are there physical dimensions to take into account (diameter, lead pitch, ..)? Any pointers or specific replacement part details would be highly appreciated.

One more question: I need a replacement 1.5A 32V main fuse, but I can only find higher voltage (250V) rated ones. In my simple mind fuses are about current so it should be OK - but again I would like to double check.

I'm aware of discussions on whether or not to rebuild the amp - but I would like to give it a shot myself and keep things original. Any guidance on the above questions would be highly appreciated!

Last edit: apologies if this question would fit better in the Parts, Service, Maintenance & Repairs section. Moderators please feel free to move this.

[pianotuner steveo]

Before you replace anything, have you reflowed solder? These amps are famous for cold solder joints...

If changing electrolytic caps, be sure you note the polarity, and put the new ones in the right way.
The black stripe running down the side of can caps indicates polarity.

I'm 90% sure wv35 means "working volts-35"

[fozziemusic]

Thank you very much! I found the same information on WV and was about to update my request / opening post, so thank you for confirming.

I will double check the joints, but thought it was good to change those 40+ electrolytic caps anyway. I am aware of the importance of the correct polarity, but again thanks for the advice!

[fozziemusic]

I've found this quote on another board:

There's a very high impedence on the reed bar, and if you don't have a good meter with a high internal impedence, the DC reading can appear lower than it really is. If you're reading any voltage at all on the preamp, it would seem there's not a short between the reeds and reed bar.

Could this be correct? I have a cheap DMM (measuring close to 55V - what was reported by the OP on the other board), so could it be that the voltage is actually correct on the reed bar but I get a low reading because of the high impedance of the reed bar and relatively low impedance of my DMM?

[pianotuner steveo]

I don't think so since you measure the voltage right where the wires attach. If you are super careful, you can disconnect the + wire from the reed bar and measure, but watch out for shorting it or getting zapped! You can disconnect it with the power off and use electrical tape to tape it to your meter...you can just leave the ground wire where it is. This will give you a reading with no load.

[fozziemusic]

That's great advice, I'll do that later tonight or when I have the chance.

As I was reading into possible issues and solutions last night, I found posts on strike line as well and in all these years I had never tried to adjust it (I did do a voicing by slightly bending reed bar and positioning reeds using gauge feelers). And how great - I was always missing that classical wurly 'sweetness' in the tone, my wurly sounded a bit more hard and piano-like. Now I have loosened the harp bolts, shifted the high side first and lower side later, and what a difference! A few minimal tweaks make all the difference! The sound is clearer, the classic wurly 'sweetness' (don't know how to describe it) is there much more now. Good stuff :-)

[pianotuner steveo]

I was thinking of "non A" models, without the preamp. I'm not sure if this changes what I recommended to try or not.

[fozziemusic]

I found I would need to desolder the + lead to the reed bar (there was a defect there when I bought it many years ago, not sure if this was one of the tiny soldering repairs I did to get back to work more or less normal). Alternatively I could try to take off the lead on the amp board at the +150v point, but it is difficult to get to and I'm a bit scared to damage the board by disconnecting the connectors which are stuck on super tight. So I'm still a bit on the fence about what I'll do, but i'll probably recap it anyway for safety after 40+ years and see where it gets me.

I've learned a lot getting here, now only a few final bits on getting the right detailed specs on the electrolytic caps (lead pitch on the smaller ones, physically fitting replacements for the large cans which seem to have 3 snap-in terminals each).

[fozziemusic]

Further update on my wurly - I noticed that there were quite serious ground loop issues with my wurly as has been reported here by others. Having the wurly off and plugging it into my twin reverb gets me a loud hum, until I disconnect the main ground (not recommended for safety of course). Wurly on the same effect. Changing grounding connections in the wurly had no effect, wurly and amp connected to the same wall socket so wasn't sure what else to do until I noticed that ground loop isolators are available for very little money.

A super cheap amazon ground loop isolator (sold for car use - similar to this one for some 6 euro or so https://www.amazon.nl/tomzz-Audio-5800-081-interferentieonderdrukkingsfilter-20-20-000Hz/dp/B00PWMVSQQ/ref=sr_1_26?__mk_nl_NL=%C3%85M%C3%85%C5%BD%C3%95%C3%91&crid=2SQ8G00EEUXC3&dchild=1&keywords=ground+loop+isolator&qid=1622137916&sprefix=ground+loop+iso%2Caps%2C157&sr=8-26) fixes all of it. Now there is a bit of hiss from the wurly when it's turned on, but not a lot at all. It may not be hi-fi, studio grade or anything, but it works wonders!

[Kevin Odhner]

The following comment from 2021 about adjusting the strike line intrigues me to no end. But which bolts were loosened, exactly how was it tweaked and adjusted? Do 'high side" and "low side" refer to the left and right halves of the reed bar, or the upper and lower pickup plates? Were they shimmed or what? What is meant by "first" and "later".

"Now I have loosened the harp bolts, shifted the high side first and lower side later, and what a difference! A few minimal tweaks make all the difference!"

If anyone remembers this post and knows what was done, I'd love to try it!

[velo-hobo]

You'd have to get a response from OP to really know what they meant with their words, but I assume if the post was about broadly adjusting strike line, "high and low" means treble and bass ends of each harp. If the strike line for a whole bunch of reeds is off, as opposed to a single reed, then that may indicate the harp is not optimally aligned to the action.

There is a little bit of left-right/front-back adjustment of the harps available when loosening the harp mounting screws and nudging things around in the horizontal plane. This is a necessary check on reassembly if you've removed the harps for any reason during other service.

You can't really fully check the results of this type of adjustment without properly tightening the harp screws back down - it's like tuning a reed in that way. So it can be a trial-and-error process.

If you get into this, be careful to pay attention when tightening those screws. I find it helps to play the piano as you are proceeding with that task so you can listen to how the sound may change. If you under- or overtighten the harp screws it can make reeds sound dull, choked or uneven. This could be user error or you might need a shim. I have never needed to shim a harp mount, but here is from the 200-series manual on that task:

You cannot view this attachment.

Another wrinkle - my 200 isn't at the house right now, but I seem to recall all the harp bushings on a 200 series are nylon. On my 140B and my 720, all bushings are nylon except the four at the left side of the treble harp are rubber. I am unsure if this was intended as a means of damping out unwanted resonances or affording twist adjustment without shims, but those would be my guesses. These are squishy so it's easy to accidentally overtighten them. And when the get old, they probably either deform, harden, or both. But I haven't had any motive thus far to change those on my pianos or others I have serviced. I don't think replacements are available other than the nylon ones anyhow.

(Adding, there is no adjustment for the pickup mounting. I don't recommend touching that assembly at all unless you are adding reed bar shields, or there is some other issue that requires it.)