Tantalum decoupling caps

[RoadrunnerOZ]

I will check the gunk again when I have the time for it, take pictures and start a topic... about motorgunk.

Is your motor 220V or 240V? Or is it 110V on a step down?

 

[PermO]

240V Hammond L100 from Belgium factory (wrecked)

 

[RoadrunnerOZ]

240V Hammond L100 from Belgium factory (wrecked)

Ok

 

[Erlend Sæterdal]

They are little bombs waiting to happen. Replace with new caps, that generally have lower esr, on a par with the tants.

Have hundreds of them are they useless ? Can make closed speakers sound boom boom like basreflex.

 

[Disco Volante]

You could probably sell them over on diyaudio as vintage hi-end caps. Some people actually believe in tants

 

[Newmarket]

Have hundreds of them are they useless ? Can make closed speakers sound boom boom like basreflex.

No. They are fine when fitted polarity correct and where they are protected from the faul conditions outlined in this thread.
If they weren't of any use then they wouldn't be manufactured in their thousands.

 

[Tubetec]

I missed out on getting a tonewheel hammond with transistorised electronics as scrap ,

Anyway best thing is megger the motor , make sure you havent a leakage to case or across adjacent windings ,
The windings can often be impregnated with varnish , thats no problem , that will all clean up nicely .

If you want to dismantle the motor use a dot punch to make reference marks on the end covers before you take it apart , so its all goes back together precisely as it was .

The Hammond on off switch board has two toggles , one starts the electronics and supplies the main motor run winding , but it only spins up when the second momentary action toggle engages the start winding , I have no idea what modifications you've done , but the start winding must be disconnected after the motor spins up or it could cause a heat issue .With a single toggle your probably cooking the start winding

Im going purely on memory of the C-3 we had in a studio I worked in almost 30 years ago
I didnt check the schematic ,I think the L-100 is very much the same .

 

[PermO]

Ah ! ding ding ding !

That must be it, I just flip it on with a single switch.

Somebody at some point put a car ignition key starter on the organ, but I did not have the carkey.
Makes so much sense now as that is a two stage switch.

Thanks for this !

Bedtime now but I'll keep you posted on this.

 

[abbey road d enfer]

Is it a B, C, L or M.
B and C have two separate switches. L and M have a single switch. The motors are different.

 

[RoadrunnerOZ]

The Hammond on off switch board has two toggles , one starts the electronics and supplies the main motor run winding , but it only spins up when the second momentary action toggle engages the start winding , I have no idea what modifications you've done , but the start winding must be disconnected after the motor spins up or it could cause a heat issue .With a single toggle your probably cooking the start winding

The L and M normally have single start motors - there are various Hammond models that have dual switches and a separate start motor, if yours has a single switch then it was fitted with a self start motor .

 

[Tubetec]

Could be a centrifugal switch on the motor shaft , sometimes they become damaged or stuck , can be difficult to find the right part to fix it .
The two position ignition style keyswitch is well suited to a repair job ,but check the voltage rating .
Having a key to start the machine up would very cool though ,

 

[RoadrunnerOZ]

Ah ! ding ding ding !

That must be it, I just flip it on with a single switch.

Somebody at some point put a car ignition key starter on the organ, but I did not have the carkey.
Makes so much sense now as that is a two stage switch.

Thanks for this !

No two stage switch on L100 - there are 250V single pole key switches readily available from most electrical wholesalers:

https://www.ebay.com.au/itm/166389558070Edit: the one above is double pole

 

[RoadrunnerOZ]

Could be a centrifugal switch on the motor shaft , sometimes they become damaged or stuck , can be difficult to find the right part to fix it .
The two position ignition style keyswitch is well suited to a repair job ,but check the voltage rating .
Having a key to start the machine up would very cool though ,

The machine is running ok, starts fine, runs fine, the motor just gets hot.

 

[gar381]

thanks all for sharing.

I'm gonna go with replacing with Panasonic fm/fm for peace of mind, also Newmarket is right there is probably lots of additional ceramics decoupling at the chip.

You should check out Panasonic FR series for rails

 

[RoadrunnerOZ]

The machine is running ok, starts fine, runs fine, the motor just gets hot.

In addition:
There is no centrifugal speed regulator - the speed of a synchronous motor is set by the number of poles and the mains frequency.
(Hz x 60 x 2) / number of poles = no-load RPM.
The rotational rate of the tone wheels is set by gearing.
From the L100 service manual:
“MOTOR AND POWER SWITCH. - The tone generator assembly, in which all tones of the organ originate, is driven at constant speed by a self starting synchronous motor, operating at 1800 RPM, located at the left side (rear view) of the console (Figure 1-2).
(In 50 cycle organs, the generator speed is 1500 RPM).
A toggle switch (Figure 1-1) controls power to the organ.”

 

[PermO]

https://groupdiy.com/threads/idea-with-old-hammond.79989/page-4
Let's go there, there's also some pics of the motor

 

[RoadrunnerOZ]

https://groupdiy.com/threads/idea-with-old-hammond.79989/page-4
Let's go there, there's also some pics of the motor

Ok done. Sorry about the hijack guys.

 

[Steven Paris]

Be aware that tantalum caps in the audio path definitely DO have a sonic signature---some like it and some don't. Neve mixing consoles of the 70s were full of them and they are reputed to be some of the very BEST sounding consoles ever made. Many have reported that replacing the tantalums with regular electrolytics ruined the "Neve sound"; also reputed to enhance the sound of some guitar amplifiers. Tantalums are also famous for often shorting out when used as power supply bypass caps, and causing massive failures (Ampex ATR-124, for example)

 

[RoadrunnerOZ]

Be aware that tantalum caps in the audio path definitely DO have a sonic signature---some like it and some don't. Neve mixing consoles of the 70s were full of them and they are reputed to be some of the very BEST sounding consoles ever made. Many have reported that replacing the tantalums with regular electrolytics ruined the "Neve sound"; also reputed to enhance the sound of some guitar amplifiers. Tantalums are also famous for often shorting out when used as power supply bypass caps, and causing massive failures (Ampex ATR-124, for example)

Over-level in the signal path, spiking due to clipping and chip failure can cause failure in tantalums just as it can in supply rail situations. They simply cannot handle overvoltage or reverse voltage. With a reverse voltage applied, a reverse leakage current flows in very small areas of microcracks or other defects across the dielectric layer to the anode of the capacitor. Although the current may only be a few microamps, it represents a very high localized current density which can cause a tiny hot-spot. This can cause some conversion of amorphous tantalum pentoxide to the more conductive crystalline form. When a high current is available, this effect can avalanche and the capacitor may become a total short.
The ability of these capacitors to withstand overvoltage for example nominally given as 1.3 x the rated voltage at 25degC reduces rapidly to below rated as the capacitor reaches its maximum rated temperature, the withstand voltage of a capacitor falls below rated at some point on the temperature axis and with a lot of circuits using a 25V cap across say a 16V rail this can cross over if the ripple current heats the cap internally enough to drop the failure voltage to rail value. In audio equipment which does not have cooling fans the ambient temperature can sit anywhere between 40 and 60degC often higher especially in recording consoles with vertical PCBs in a trapped air environment which can stay running for months - add the ambient to operationally induced heat and the temp can easily climb over the maximum. Any adjacent components which may overheat without failure can locally transfer this heat to tantalum caps and cause their failure.
It’s not just the standard room temperature voltage rating that is important but also the voltage/temperature rating curve - and thus following, the voltage rating at the operating temperature of the circuit the cap is in - this applies to any capacitor. Circuit design did not include this factor for the old gear - experience and factory recalls, service history etc. all contribute to changes which led in a lot of cases to the exclusion of the use of tantalum capacitors.
The series parasitic inductance of through hole tantalums can be higher than for equivalent can electrolytic caps. Low ESR electrolytic can caps are readily available and would mimic the sonic characteristic of the tantalum.
Also replacing old tantalums from the ‘70s and ‘80s with new like for like tantalum caps does not guarantee the same sonic signature - the new tantalums are made with different processes and electrolytes to the original failure prone ones - but they still have more constraints than good old can electros.
Rupert Neve did not stop designing and making good consoles because of a change from tantalums - there are too many multi platinum albums that are out there still getting airplay and still being touted as sounding amazing and still today music is being recorded and mixed on the same consoles to make the “can electrolytics ruined the Neve sound” statement hold any real water. The so called “many” who have reported that could be outweighed by all the world class engineers, producers and studio designers who would disagree. If the older desks sounded that much better no studio in their right mind would have forked out the huge sums of money the newer consoles demanded.

 

[CalavoBob]

Here's a story about poor application of tantalum voltage ratings. I used to manage the repair shop for a audio-video manufacturer.

One day the service techs started receiving phone calls about some of the editing systems exhibiting a stuttering in the video picture. Over the next several days similar calls were received, but during the following week some customers called with a similar problem that resulted in circuit boards that were actually burning up part of the circuitry. A number of the units were sent to our department by customers and we began studying them.

Just like they described, we were seeing a stuttering in the video image on these boards after about 5 to 10 minutes of warmup time, but we could not figure out what was causing it. The basic signal check points did not show anything wrong. Then we received 3 boards in which the entire bottom right of the circuit board had a burned-out area covering about a dozen of the surface mounted components. The area was so badly damaged that we couldn’t figure out what was causing it.

When I tested the next board, we got lucky. This board had no visible damage, but moments after I plugged it in, one of the tiny surface mounted tantalum capacitors around the voltage regulator blew up before my eyes! I saw exactly which one it was. I took out another board that wasn’t burned yet and with careful inspection I discovered that the capacitor that blew up was rated at 6 volts, but it had 12 volts across it! Right next to it was a similar looking capacitor rated at 12 volts but it only had 5 volts across it. Clearly these 2 capacitors had been swapped from their correct positions.

A look at our shop schematics showed the problem. There had been a redesign of the circuit board that month and one of the changes had been the positions of those 2 capacitors. Our shop files contained an Engineering Change Notice (ECN) that had told us about this change and indicated that it had happened 3 weeks ago. We checked with the technicians running the pick-and-place circuit board assembly line and to our surprise found that they had not been included in the list of departments who received the ECN. They never knew to change the position of the two capacitors. We had been sending out a faulty product for 3 weeks. The ECN did however list the serial numbers of the boards that should have been changed, so we were able to contact customers to have them return their boards for service. There were about 350 boards that we had to replace the capacitors on, and 7 boards that we had to completely replace because of heat damage. The hidden damage is also the mark it puts on the reputation of a company when something like this happens.

The solution here is that any change in the production of a manufacturing product needs to be carefully documented and then every department in the company needs to receive a copy the Engineering Change Notice. It certainly could have prevented the problem, but even after it happened it was the ECN that enabled us to fix the problem as soon as possible. The complete distribution of the ECN’s around the company needs to be a strong company policy.