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Tremelo parts (light bulb) [message #3161] Tue, 14 October 2003 01:43 Anonymous Hi, I'm resurrecting a Frankenstein head, and it seems that the light bulb that controls the optical resistor, in the tremelo circuit is completely open (infinite resistance). The oscillator circuit seems to be working OK. Has anyone ever replaced those parts (the bulb and opto-resistor inside heatshrink)? And, if so, what did you use for replacements? I think I might have to jerry-rig this whole opto-isolator apparatus. I'm doing all of this without a schematic. Any help would be appreciated. Report message to a moderator

Re: Tremelo parts (light bulb) [message #3165 is a reply to message #3161] Wed, 15 October 2003 14:11 Anonymous I recently rebuilt the vibrato in one of these heads. The light bulb was a #48. It had wires soldered to the threaded base. My book says that a #48 bulb is 2 volts at 0.06 amps. If you can't find one, a #49 is the same specs but with a bayonet base. The CdS photocell was a Clairex CL-603. The vibrato was very weak, so I replaced the photocell with one that I had around. I tried 5 or 6 different cells to find the one that worked best. Hope this helps. Bill from Chicago. Report message to a moderator

Re: Tremelo parts (light bulb) [message #3166 is a reply to message #3161] Wed, 15 October 2003 14:13 Anonymous I recently rebuilt the vibrato in one of these heads. The light bulb was a #48. It had wires soldered to the threaded base. My book says that a #48 bulb is 2 volts at 0.06 amps. If you can't find one, a #49 is the same specs but with a bayonet base. The CdS photocell was a Clairex CL-603. The vibrato was very weak, so I replaced the photocell with one that I had around. I tried 5 or 6 different cells to find the one that worked best. Hope this helps. Bill from Chicago. Report message to a moderator

Re: Tremelo parts (light bulb) [message #3168 is a reply to message #3166] Thu, 16 October 2003 07:46   stevem Messages: 4733 Registered: June 2004 Location: NY Senior Member Hi,you might find that a opto/resistor setup from the ampwares site may work?I have a frank head also but I,ve never been into it to realy check out the tremlo circuit. Report message to a moderator

Re: Tremelo parts (light bulb) [message #3192 is a reply to message #3161] Mon, 27 October 2003 14:27   Roy Messages: 11 Registered: June 2004 Junior Member Thanks for the help, I used the CM-49 bulb, it worked fine. Report message to a moderator

Re: Tremelo parts (light bulb) [message #3194 is a reply to message #3192] Tue, 28 October 2003 11:28 chicagobill Messages: 2005 Registered: April 2003 Senior Member Roy: Glad to hear that you got it working. Just out of curiosity, was your original bulb a #48? Does your amp have tremolo or true vibrato? Bill Report message to a moderator

Re: Tremelo parts (light bulb) [message #3195 is a reply to message #3194] Tue, 28 October 2003 13:46   Roy Messages: 11 Registered: June 2004 Junior Member Bill, Yes, the original lamp was a 48 lamp. The amp seems to have tremelo (varying volume) as opposed to vibrato (varying pitch). It's a very soft sounding vibrato. Now if I could only get the crazy noises out of that channel of the amp. The normal (no effects) channel is perfectly quiet though. Thanks for your help! Oh, by the way, I measured the original photocell resistor in circuit; it measured around 6K ohms with full illumination, and around 7M ohms with no illumination. Roy Report message to a moderator

Re: Tremelo parts (light bulb) [message #3196 is a reply to message #3195] Wed, 29 October 2003 11:18 Anonymous Roy, Glad I could help. Mine is true vibrato (pitch shift), which was very weak until I changed the photocell. The new one made a big difference. What kind of noise is your amp making? Bill Report message to a moderator

Re: Tremelo parts (light bulb) [message #3197 is a reply to message #3196] Wed, 29 October 2003 19:33   Roy Messages: 11 Registered: June 2004 Junior Member Hi Bill, I think the noise is generated in the pre-amp section. When I crank the volume and tone controls I get a low rumbling oscillation from the bass control and a lot of hiss from the treble control. The other channel does not make those sounds when cranked. I was going to put a scope on it and try to figure out where it is being generated. Any help would be appreciated. Thanks, Roy Report message to a moderator

Re: Tremelo parts (light bulb) [message #3199 is a reply to message #3197] Thu, 30 October 2003 11:19 chicagobill Messages: 2005 Registered: April 2003 Senior Member Roy: The low freq. osc. could be filter cap related. Check the filter and bypass caps on the preamp board. I've found that most hiss is transistor or IC related. Bill Report message to a moderator

Re: Tremelo parts (light bulb) [message #3296 is a reply to message #3199] Wed, 03 December 2003 13:43 John Messages: 1 Registered: December 2003 Junior Member Hi-I'm trying to fix an old Frankenstein head M/n J595 RV S/N 10948. The problems I,m having are just as people on the site have described-reverb that reduces volume without any reverb effect and intensity and speed knobs that do nothing. Thanks to what I learned on the site I've purchased a Clairex CL-603 photocell and a # 49 lamp from Mouser. I haven't opened up the amp yet and I believe schematics are non-existent. Any words of advice before I begin? Thanks Report message to a moderator

Re: Tremelo parts (light bulb) [message #3297 is a reply to message #3296] Thu, 04 December 2003 12:09 chicagobill Messages: 2005 Registered: April 2003 Senior Member In 595 RV heads, the reverb and vibrato circuits are both located on one circuit board located on the left side (when viewed from the front) of the amp. The reverb control works differently from most amps, as it is really a balance control. Full counter-clockwise all straight signal, full-clockwise all reverb signal. Therefore what happens when you turn up the reverb, you turn down the straight signal. If you've already checked the tank and wiring, check the transistors and the caps in the reverb circuit. Good Luck! Bill from Chicago. Report message to a moderator

Re: Tremelo parts (light bulb) [message #3298 is a reply to message #3161] Thu, 04 December 2003 14:04 beagle Messages: 12 Registered: September 2003 Junior Member I have a similiar problem with my K-200 head. I get reverb when i turn the pot up, but when I combine that with the speed pot turned up, all I get is dramatically reduced volume levels. Can anyone tell me what's wrong? Report message to a moderator

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