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Thread: Having trouble with my Vibrato and line box on the a100

  1. #11
    pp Pianissimo PGR's Avatar
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    Really sorry Enor I did not remember I had indicated it was an A100 It is in the title !! guess I should be more observant

    I did a meter check following Davids thinking ( all good ideas get tried) Here s what I found that I did not expect.. I grounded out my meter and tested around, both AC and DC! The pre amp box is carrying 6 mV ac to ground so is the power amp and the percussion amp as well as the TWG is too The line box is carrying about 4- 5 mV ac on the ends of each cap generally speaking. but not the housing to the vibrato scanner - it was zero. This was tested with the V1 c1 set to v1 The more I listen to the vibrato from the line it seems ok but very weak and likely because caps have never been upgraded however the scanner is really choppy - How do I start to review that. ?

    I have read that some shock the terminals of the scanner - don't know if this is going to work for me but wondering if a BBQ starter would provide enough juice to shock it to life? rather than holding two 9v together? any comments.

    The recapping of the TWG which is where I started sounds bright like I wanted it and I have fuller clarity in the tones generated big difference here. I had trouble with my leslie leaking current I wonder if that applies to the a100 too?


    Also When I checked the TWG after putting it back in I noticed that one of the tones generated is not sounding this is fre 29 and it does not show on either manual it is only on each amnual on the second E It sounds every where else. When I found which lug it was I put the scope on it and I do get a a freq reading which is close and I get RMS readins reasonable close etc. When I put on the external speaker on the lug I get nothing like at the key board manuals. Some thing is not correct in my readings because I don't think this is possible ..getting a scope reading but no sound generation ? your thoughts guys. oh for got to mention the ampl is not in the right range

  2. #12
    fff Fortississimo jdoc's Avatar
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    1 members found this post helpful.
    you don't hold 2 9v together, you clip one (+) to one (-) then get 18volts series off the other two terminals, some go 27V
    1956 M3, (2)51 Leslie under upgrade, 860 (130 powered)Leslie with Preamp, S08 Yamaha and two K2000S, Young Chang spinet, Korg Trinity
    and Korg KRONOS X73
    Looking for that mythical cheap or free A, BV, CV, C2, C3 or A100 but wouldn't say no to a free B3

  3. #13
    pp Pianissimo PGR's Avatar
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    OK so + to - and + to - and + to - givs 27V so if the BBQ starter gives at least 18 I should be in the right range Don't know what it gives but I will measure it.

  4. #14
    fff Fortississimo David Anderson's Avatar
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    Quote Originally Posted by PGR View Post
    I did a meter check following Davids thinking
    I had suggested that you check (with the organ off) the DC resistance from chassis ground to various line box and scanner harness terminals, but somehow that turned into checking voltages.
    I'm David. 'Dave' is someone else's name.

  5. #15
    ff Fortissimo enor's Avatar
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    Before you go crazy changing caps more or less at random, and zapping:

    De-solder the connections to terminals A and B on the preamp. Reverse them and solder them back the other way around. This reverses the action of the vibrato tablets, and one out of two scenarios will follow:

    1. You will now have faint non-vibrato sound, and normal volume on the vibrato sound (albeit with the switches in the "vibrato off" position). In this case, your problem is in the wiring up to the preamp.

    OR

    2. You will still have the same faint vibrato (albeit with the switches in the "vibrato off" position). In this case you can carry on troubleshooting along the lines you've started.


    If #2:

    * Solder the two wires back the way they were. De-solder the wire from terminal C (this is the feed to the delay line). Play a note with the vibrato tabs "on", and check if you have signal at terminal C. "No"? Your problem is in the vibrato stage of the preamp. "Yes"? carry on.

    * Since the percussion and non-vib channel works, we already know that the recovery stage is ok

    * NOW is the time to start looking at the scanner/delay line.

  6. #16
    pp Pianissimo PGR's Avatar
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    HI David,

    I tested with the ohmmeter and an voltmeter everywhere like suggested and in general I have 6 mV everywhere except the line box which turns out to be 4.6 mV to 5 or so except for the last two or three caps near the red and blue wires. the scanner points are all about the same mV. On all the metal boxes ,twg, the power amp, pre amp and percussion I get a very steady 6mV even on the lugs I get this 6mV except for one tone freq 29 which drops to the 4.4mV
    Is 6mV a normal number?

    On the ohms side My numbers are a long way off the 10K suggested The twg box is 1.4 to 1.1 Ohms pre amp box is 2.8 ohms, percussion box is 3.2 ohms power amp is 3.3 ohms directly to ground Within the organ - not outside the organ I also tested some of the points on the scanner and the numbers I got are 45 ohms at the easiest to reach point next to it 129ohms counter clock wise, next same direction is 200 ohms can't reach any more in that direction so from the top clockwise are 201 ohms and then 195 ohms Is this indicative of a bad /dirty scanner ? and is the remedy to remove it and clean it as suggested?

    Problem 2 ; Freq 29 : This tone wheel has no sound at the lug. both manuals on the second E note do not have a tone. with only the third harmonic drawbar in any drawbar set pulled out . If you pull other drawbars out and test this E on either manual I get a sound. I have yet to lift the TWG and see if this tone wheel is turning - it was before I pulled out the TWG. Also when I scope the tone at the lug I get readings similar to what I have recorded which suggests it is generating a freq. When I test the lug with my exterior sound amp - I get no tone generation only a hum .

    - - - Updated - - -

    update on the BBQ starter it only gives 1.2 - 1.5 volts not enough!

  7. #17
    pp Pianissimo PGR's Avatar
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    David and Enor:

    When modifying anything It is always good practice to go back and be sure the basics are covered first. I did that and found that the shielding on the vibrato input from the scanner and the line to the pre amp was not very good. I sanded all the points and screwed the ground strap/shielding back together and viola The vibrato is back to being correct or at any rate the same way it was before. Volume does not change between on and off. no wash boarding on the scanner vibrato I get the 10K ohms as expected everywhere - it is within reason anyway but 9.6 K to 10.2K this is good Right?

    - but I will be honest and say that the difference between the scanner and line vibrato is almost non existent. I probably need to clean the scanner and replace caps on the line vibrato anyway. What should it sound like ?...I know you likely can't describe it but is it different enough to hear?

    If I did clean the scanner and recap the line , would that change the fact that these two systems almost sound the same? Would they then sound different?

  8. #18
    ff Fortissimo enor's Avatar
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    Hm. What do you mean by "line vibrato" (what are you comparing it to?)

  9. #19
    pp Pianissimo PGR's Avatar
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    Quote Originally Posted by David Anderson View Post
    Did you disassemble, clean, and reassemble the scanner while the TG was out? It's a good idea to do this while the TG is out of the organ if it has to be removed.

    Put the V1-C3 knob on one of the V positions, put one end of an Ohmmeter to ground, and test the various line box and scanner terminals. You should find ~10k everywhere, typically. If you have less than that, you have a short somewhere.
    Quote Originally Posted by David Anderson View Post
    I had suggested that you check (with the organ off) the DC resistance from chassis ground to various line box and scanner harness terminals, but somehow that turned into checking voltages.
    These are the comments I was responding to David but I missed where you said turn off the organ. Maybe I just missed the meaning What I was getting at with my test is that there seems to be a current flowing around everything and I did not know if this was correct.

  10. #20
    pp Pianissimo PGR's Avatar
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    Enor, I understand you have a lot of experience with the vibrato circuits and can likely steer me right. When I cleaned the grounding points to the Pre amp of the vibrato switches etc I got a much more even (volume) between no vibrato and vibrato on with both manuals. I have not recapped the line box (line vibrato) my apologies here because I guess I don't understand how the mixing of vibrato down the line box is impacted by the input of the scanner.

    What I do notice is that there is minimal difference between say c1 and c2 or c2 and c3 or even 1 and 3 AND if I put in the mix and of the V1;v2;V3 I get pretty much no change. I am assuming that the introduction of the v's is the triggering of the vibrato scanner into the mix? If this is not correct straighten me up please.
    I would have expected there to be a clearer difference in the steps achieved by switching through the v1 c1 v2 c2 etc

    Would this difference be clearer if the line box were recapped? and I guess the scanner cleaned ?
    Before I go to the trouble of this work I should try to understand what the system should sound like ( can you suggest something I can listen to that would help me?)

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