Author Topic: rhodes 5-pin vibrato issues - intensity affects volume?  (Read 131 times)

Offline Tom999

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rhodes 5-pin vibrato issues - intensity affects volume?
« on: November 14, 2020, 06:14:34 AM »
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  ;D. 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

Offline Jenzz

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Re: rhodes 5-pin vibrato issues - intensity affects volume?
« Reply #1 on: November 14, 2020, 09:48:42 AM »
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
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Offline Tom999

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Re: rhodes 5-pin vibrato issues - intensity affects volume?
« Reply #2 on: November 15, 2020, 05:24:23 AM »
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

Offline Jenzz

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Re: rhodes 5-pin vibrato issues - intensity affects volume?
« Reply #3 on: November 15, 2020, 10:57:14 AM »
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
Rhodes tech in Germany
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www.spontaneousstorytelling.net

VintageVibe 64 ACL + DOD FX25B, Tone City Sweet Cream, Rocktek PHR-01, Boss BF-2
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Offline Tom999

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Re: rhodes 5-pin vibrato issues - intensity affects volume?
« Reply #4 on: November 15, 2020, 02:07:11 PM »
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!

Offline Jenzz

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Re: rhodes 5-pin vibrato issues - intensity affects volume?
« Reply #5 on: November 15, 2020, 03:32:17 PM »
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
Rhodes tech in Germany
www.tasteundtechnik.de
www.spontaneousstorytelling.net

VintageVibe 64 ACL + DOD FX25B, Tone City Sweet Cream, Rocktek PHR-01, Boss BF-2
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Offline Tom999

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Re: rhodes 5-pin vibrato issues - intensity affects volume?
« Reply #6 on: November 15, 2020, 03:52:40 PM »
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.

Offline Jenzz

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Re: rhodes 5-pin vibrato issues - intensity affects volume?
« Reply #7 on: November 16, 2020, 02:45:54 AM »
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
Rhodes tech in Germany
www.tasteundtechnik.de
www.spontaneousstorytelling.net

VintageVibe 64 ACL + DOD FX25B, Tone City Sweet Cream, Rocktek PHR-01, Boss BF-2
Adams Solist 3.1 Vibraphone

Offline Tom999

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Re: rhodes 5-pin vibrato issues - intensity affects volume?
« Reply #8 on: November 17, 2020, 05:17:08 AM »
I'll give them a shot. Worst case I order a couple of the VTL5C1s.  Thank you