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T500 Leslie (Tremolo) Slow/Fast switch loud bang on switching

paul_english All Messages By This Member #83318 Hi,? when switching slow to fast or vice versa on the red Tremolo switch, there is quite a bang through the speakers. I seem to remember that a while ago my local organ tech (now retired) advised it may be a capacitor on the amplifier though I didn't get the details.? ?I have the T500 service manual and I think I can work it out from there if someone can point me in the right direction. Many thanks. ? By the way I downloaded the manual from a website called archive.org.? ? ?
Brendon Wright All Messages By This Member #83319 Hi Paul! I'm not at the same location as my service manuals at the moment, but I strongly suspect that if your T500 is still in reasonably original condition that you'll be able to find a capacitor across the leslie switch itself which will need to be replaced. It swallows the "spit," the spark that jumps between the contacts the moment before contact is made. It's probably a low value like 0.1uF or even 0.01uF, but it'll bridge the switch. The voltage at that switch is probably?about 12V. Now I think about it, there's also one across the relay, hidden inside the amp chassis. That voltage is 120/240V. If you don't feel up to going under the chassis you could even put one across the 5 pin leslie plug, providing you can identify the two power pins. Oh. Now I recall FURTHER, (it's been 12 years or more) there's three power pins at that plug, one going to fast, one to slow, and one common, so you'd need two capacitors if you were doing it there, one for each pair, whether the slow or fast motor is being engaged. It's been a year or two since I've fooled about with all this stuff!I asked?Chris SO many questions back then. Best wishes, -Brendon Wright toggle quoted message Show quoted text On Wed, 1 Jan 2025 at 08:50, paul_english via <paul_english=yahoo.com@groups.io> wrote: Hi,? when switching slow to fast or vice versa on the red Tremolo switch, there is quite a bang through the speakers. I seem to remember that a while ago my local organ tech (now retired) advised it may be a capacitor on the amplifier though I didn't get the details.? ?I have the T500 service manual and I think I can work it out from there if someone can point me in the right direction. Many thanks. ? By the way I downloaded the manual from a website called .? ? ?
Chris Clifton All Messages By This Member #83320 开云体育 Underneath the amplifier chassis, near the speed control relay there is a suppressor network consisting of two 0.1uF capacitors and a small resistor (33 ohm if I recollect). At least one of those two capacitors has failed short circuit resulting in the resistor burning out. This was quite a common fault on T-series organs, I'd replace both capacitors with modern X2 suppressor capacitors and replace the resistor with a new 1/2 watt resistor of the correct value as shown in the schematic. X2 rated capacitors are specifically designed for use in this type of suppressor network, standard capacitors tend to fail when subject the high voltage impulses generated when motors are switched. To gain access to the underside of the amplifier chassis, you'll need to undo all the wire ties holding wiring to the front of the organ above the chassis. when the wires are all loose, undo the four screws at the corners of the chassis and carefully lift the chassis out and tilt it towards you. On 31/12/2024 19:50, paul_english via groups.io wrote: Hi,? when switching slow to fast or vice versa on the red Tremolo switch, there is quite a bang through the speakers. I seem to remember that a while ago my local organ tech (now retired) advised it may be a capacitor on the amplifier though I didn't get the details.? ?I have the T500 service manual and I think I can work it out from there if someone can point me in the right direction. Many thanks. ? By the way I downloaded the manual from a website called archive.org.? ? ? --
Uwe Menrath All Messages By This Member #83321 Happy new year to all! ? The Leslie control schematics show a SPDT contact set relay with a pair of 0.1 ?F capacitors (C621, C622) across the points. No resistor. Yes, due to their age these capacitors are the first suspects and can/should be replaced without measurements. But also check the suppressor diode (D607) across the relay coil. It must not be open (OL) with your DMM's red probe at the anode and the black one at the cathode. This inhouse numbered diode can easily replaced by 1N4007 or the like. ? Best regards!
paul_english All Messages By This Member #83323 Hi, thankyou for the help. I am in the UK, can you advise the best place to order the parts. ? Happy New Year to you all. cheers
Uwe Menrath All Messages By This Member #83324 In the UK, Mouser usually is the best distributor. But take care of their minimum order. ? Years ago I bought a bag full of 0.1 ?F 275 V~ X2 capacitors from a German surplus dealer for almost nothing. But they're out of stock now. ? Best regards!
Chris Clifton All Messages By This Member #83325 开云体育 The components you're looking for are C621, C622 and R699 in the schematic. Two 0.1uF capacitors and a 47R resistor. These capacitors, at CPC? would be ideal. I've got some here I could send to you. Send me an email, and we can discuss cost etc. On 01/01/2025 13:29, paul_english via groups.io wrote: Hi, thankyou for the help. I am in the UK, can you advise the best place to order the parts. ? Happy New Year to you all. cheers --
Chris Clifton All Messages By This Member #83326 开云体育 This forum doesn't display email addresses,? My email is clifton.christopher@.... On 01/01/2025 15:00, Chris Clifton via groups.io wrote: The components you're looking for are C621, C622 and R699 in the schematic. Two 0.1uF capacitors and a 47R resistor. These capacitors, at CPC? would be ideal. I've got some here I could send to you. Send me an email, and we can discuss cost etc. On 01/01/2025 13:29, paul_english via groups.io wrote: Hi, thankyou for the help. I am in the UK, can you advise the best place to order the parts. ? Happy New Year to you all. cheers -- --
Chris Clifton All Messages By This Member #83327 开云体育 My schematic shows a 47R resistor R699 as part of the snubber network, On 01/01/2025 10:36, Uwe Menrath via groups.io wrote: Happy new year to all! ? The Leslie control schematics show a SPDT contact set relay with a pair of 0.1 ?F capacitors (C621, C622) across the points. No resistor. Yes, due to their age these capacitors are the first suspects and can/should be replaced without measurements. But also check the suppressor diode (D607) across the relay coil. It must not be open (OL) with your DMM's red probe at the anode and the black one at the cathode. This inhouse numbered diode can easily replaced by 1N4007 or the like. ? Best regards! --
Uwe Menrath All Messages By This Member #83336 Well, Chris, there might be more versions that the one I've got handy. There've been also versions with electronically generated rotational fields, just like in BLDC motors. ? Admittedly, my original SM covers the T-100, T-200 and XTC series, and I was thinking there coudn't be big differences to the T-500. ? Best regards!

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