rhodes 5-pin vibrato issues - intensity affects volume?

[Tom999]

Hi Couldn't find this particular issue with search.  I'm almost done restoring this rhodes. The 5-pin vibrato technically works and I did the recap kit from avion.  I'm wondering if I'm experiencing normal vibrato behavior or if there is some work I could do to improve the response:

1) The intensity knob seems to affect overall volume. When it's at minimum, no change in volume. As I increase intensity the overall volume drops in proportion. 

2) The vibrato is noticeably louder on the left channel, I can see the levels in my mixer so it's not just my bad hearing  . At max intensity I'd say it's at about twice the level.

Is that par for the course or is there something I could check for in the circuit?

Thank you
Tom

[Jenzz]

Hi :-)

Seems that one of the Vactrol Optocouplers is bad. If the intensity pot alters the volume, the LDR in the defective channel goes not down enough in resistance when its LED is lit... Or the LED becomes not bright enough.

Did it work correct before the recab job?

Jenzz

[Tom999]

Thanks for your reply. It worked before the recap but I didn't have it setup with wide enough monitors to really notice the behavior.

The LDRs...I have a bunch of originals that I bought in 2015 when they announced they were being discontinued.  If so I can just swap it out and see if that makes a difference. Do you happen to know if the right channel is LDR1(top) or LDR2(bottom)? https://www.fenderrhodes.com/org/ch11/fig11-2.jpg

[Jenzz]

Hi .-)

If you have a bunch, i would replace them both.

BTW: Did you measure the + / - 15 voltages for the preamp coming from the cabinet? If one or both are siginficantly lower, the LEDs will be darker, too.

Jenzz

[Tom999]

Hmm..that's an idea. I also have a handful of vtl5c3/2's but looking at the circuit I don't think I could substitute that for the 2 LDRs.   I'll just replace one at time and see if that does anything. But will double check voltage first.  Thank you!

[Jenzz]

Hi .-)

Couplers should be VTL5C1... The /2 types have a dual LDR element (hence the 3 wires instead of 2) and are only used by Rhodes in the latest Mk2 Suitcase Preamp circuit ('Blackface' with all rotary knobs)...

Jenzz

[Tom999]

Shoot I only have vtl5c3's on hand. I don't suppose they are suitable to replace the vtl5c1's? I read they have a bit of light history.

[Jenzz]

Hi .-)

The VTL5C3s will work, too, but give a different character of the tremolo wave. They have an overall lower resistance, so with intensity at full, there will be a little bit of signal left.

See the PerkinElmer datasheets:

www.tasteundtechnik.de/bilder/perkinelmer.pdf

Jenzz

[Tom999]

I'll give them a shot. Worst case I order a couple of the VTL5C1s.  Thank you

[Tom999]

Reporting back in case anyone is interested in knowing if different vactrols work with the vibrato, I did install a pair of VTL5C3s and that immediately solved the volume discrepancy between channels.  They actually sound very nice!  I don't really notice a difference and they definitely perform as expected. At full intensity I don't see any signal bleeding between channels. The speed goes from super slow like before to almost a ring mod/steady tone sound.