The Electric Piano Forum

Repairs, Maintenance & Upgrades => Parts, Service, Maintenance & Repairs => Topic started by: Proudfood on June 14, 2018, 07:10:21 AM

Title: Wurlitzer 140B
Post by: Proudfood on June 14, 2018, 07:10:21 AM
I recently bought a Wurlitzer 140B that puts out very low volume with a lot of hiss/white noise, other than that everything seems to function like it should. I noticed that what I think are resistors look like they are falling apart, see the first picture. Would that cause the hiss or is that symptomatic of another problem? I have some basic experience with electronics and could switch out the parts, just want to make sure I'm headed in the right direction. I also attached a picture of the whole circuitboard. Thanks for the help.
Title: Re: Wurlitzer 140B
Post by: Alan Lenhoff on June 14, 2018, 12:42:27 PM
I can't help you track down the issues you mention. (Although I suppose the low volume might have resulted from someone turning down the gain control on the amp.)  But your photos suggest all your components are original, which makes them about 50 years old.  I would suggest a re-build.

Several years ago, I re-built mine, mostly following this plan from Vintage Vibe.  I replaced all the electrolytic caps (including the filter caps in the cans), the small transistors (look for extra low-noise ones) and the power resistors. I don't believe I changed the power transistors.  The before/after difference was dramatic.  People say the 140B amp is inherently noisy, but mine sounds great, and ought to be reliable for years.

The 140B is a great Wurli. It deserves an amp working at its best.

Title: Re: Wurlitzer 140B
Post by: Alan Lenhoff on June 14, 2018, 12:45:02 PM
By the way, Vintage Vibe sells a kit with all the parts you would need:

Title: Re: Wurlitzer 140B
Post by: Ben Bove on July 12, 2018, 12:36:36 PM
I would definitely agree that this amp is a candidate for rebuild.  The electrolytic capacitors alone (black) are well past the intended life expectancy.  Even if they were quality Sprague!

The question would be if you're comfortable removing components and soldering.  If not, I would recommend a rebuilding service.  It's straightforward enough with the rebuild kit, so any decent electronics repair shop or "guitar amp guy" could do a rebuild.
Title: Re: Wurlitzer 140B
Post by: wolfpup on July 08, 2019, 10:57:26 AM
Hi, all I'm new to this site  and i know this thread is a bit old,  but i have a 140B that came in for repair, has a loud hum sound that will increase with volume control.  i can hear the keys as well,   if i unplug the pickup  (RCA cable) the hum go's away and the amp is quiet as a mouse.   i plugged in a  MP3 player  and the sound is clean.    some kind of pickup problem ?

let me know what you think Also    i changed out all the caps already  but nothing else.

Title: Re: Wurlitzer 140B
Post by: Alan Lenhoff on July 08, 2019, 08:02:42 PM
As an advocate of the "always try the simple stuff first" school of teching:

Is the lid removed from the piano when you hear the loud hum?  The lid on this model is painted on the inside with electrostatic shielding paint, which makes the lid a hum shield that protects the pickups from picking up external sources of hum.  These pianos will all hum like crazy if the lid is not in place. The lid also needs to be grounded. This is accomplished by tightening all its screws so it makes good contact with the grounding braided cable below the left side of the lid.  If screws are missing or the braided cable is damaged, or the lid is dented, it may not make good contact with this ground.