Console PSU recap - What about those tantalums?

[Soul One]

Recapping my TAC 750 PSU and wondered what to do with the tantalum caps. I have 3 options and would love to hear your opinion on them:

1. Leaving them alone
2. Replacing with new tantalums
3. Replacing with electrolytic caps

I've seen a video where the guy (DoItYourselfMusician) opted for option 3 and replaced the tantalums with 10u/50v electrolytic caps. Would you also recommend doing that?

Thanks!

 

[Newmarket]

Which caps are Tants ? I can see only C35 marked as such but there are other caps same value and Vdc

 

[k brown]

Personally I'd ditch them all, if at all practical. Not a single reason to keep them; they're generally considered time bombs.

 

[Khron]

Personally I'd ditch them all, if at all practical. Not a single reason to keep them; they're generally considered time bombs.

This

 

[radardoug]

Time bombs!

 

[Newmarket]

Can't agree with the anti Tant bias here. I've put them into lots of designs, so hence a lot of units in the field. Talking modern (well not that modern - say 25 years. Usually SMT TAJ series thought sometimes thru hole.) No known issues except where installed with incorrect polarity - Don't do that

 

[Khron]

And yet, they go shorted (if not even also burn up) even in stuff like Apogee Ensemble interfaces - not that old, and not subjected to reverse voltage...

 

[k brown]

I guess the best question to ask is: why use them at all? Just 'cause they're small?

 

[ccaudle]

why use them at all?

Primarily size and better low temperature (sub-freezing) performance than electrolytic.
Downside is they sometimes catch on fire. Polymer tantalum should not have that problem, but more expensive.

 

[radardoug]

They short out and they burn up. Two very good reasons for not using them.

 

[Newmarket]

And yet, they go shorted (if not even also burn up) even in stuff like Apogee Ensemble interfaces - not that old, and not subjected to reverse voltage...

That doesn't sound great. Do you happen to know manufacturer / series / values ?

 

[Khron]

I recall they were yellow, but that's about it.

https://khronscave.blogspot.com/2019/11/57-apogee-ensemble-firewire-pt2-repair.html
https://groupdiy.com/threads/ensemble-burnt-capacitor.50091/

 

[RoadrunnerOZ]

Some manufacturers used to put a tantalum on every IC on a board and the only way to isolate the blown ones if they didn’t have a hole in the side was to cut supply rail tracks until the rail didn’t read dead short. Had a lot of gear with blown tantalum’s due to overvoltage conditions arising from power supply failure (or someone connecting 240V to a 110V machine), power on spikes, line spikes from air-conditioners and industrial fridges sharing stage power at gigs. Tantalum’s just can’t handle overvoltage or overcurrent. If using them anywhere in a power supply they should rate at 3 x the operating voltage.
Worth a read:
https://www.utmel.com/blog/categori...-explosion-and-burning-of-tantalum-capacitors
NTC resistors used for soft start in power supplies also have a habit of failing but they usually end up with a big hole in the side. These can cause a problem for tantalum caps in a power supply if the power is switched off and then back on without allowing the NTC time to cool and prevent the inrush of current that it was put there for.

 

[Khron]

I think i've only seen NTC's on the mains side input of switching power supplies. If they destructively fail there, it's often down to a blown MOV and/or fried switching elements etc. Don't recall NTC's on the low-voltage DC side of things, but then again, i have yet to see EVERYthing

 

[RoadrunnerOZ]

No you’re right, they’re usually on the mains input after the switch. When they fail the transformer gives a healthy belt to the DC circuit following. I recently serviced a keyboard that had an NTC fail with an impressive bang and some nasty smoke. Caused a few capacitors to go as well.

 

[Kelvin Zero]

I'm trying to get my MCIJH636 going at the moment and I've been replacing like for like. I guess I shouldnt.
The best thing about tantalums is it's easy to find the fault. I turn on the power, listen for the fizz, then use my nose to find the module (or fader) that just blew. They usually take a few nearby parts out so are easy to find

 

[RoadrunnerOZ]

In cases where tantalums are in the audio path, like coupling caps, they should be replaced like for like as the characteristics of the circuit surrounding them are affected - if you change to a normal electrolytic it may change the sound.

 

[RoadrunnerOZ]

I'm trying to get my MCIJH636 going at the moment and I've been replacing like for like. I guess I shouldnt.
The best thing about tantalums is it's easy to find the fault. I turn on the power, listen for the fizz, then use my nose to find the module (or fader) that just blew. They usually take a few nearby parts out so are easy to find

In that photo I notice the old type red IC sockets - these age and become brittle, crack and start to fall apart and become noisy over time - they were used in the Neve 51 series (and others) and are always a suspect in noisy issues from my experience. There’s one in the photo at the top above a blue trimpot with a ua741 in it that has a crack by the look of it. Those burnt resistors look like they feed + power rails going to the toasted op-amp with a pair of tantalum’s across them.

 

[JohnRoberts]

Tantalum caps have a bad reputation for failing short circuit which can be spectacular when used across PS rails. In DC blocking applications the failures are less spectacular but still annoying. I would replace with similar value modern aluminum electrolytic.

JR

PS: Tantalum differs from other popular electrolytic dielectrics mainly in DA (dielectric absorption). DA matters for sample and hold circuits but not so much for typical audio, in my experience.

 

[RoadrunnerOZ]

Tantalum caps have a bad reputation for failing short circuit which can be spectacular when used across PS rails. In DC blocking applications the failures are less spectacular but still annoying. I would replace with similar value modern aluminum electrolytic.

JR

PS: Tantalum differs from other popular electrolytic dielectrics mainly in DA (dielectric absorption). DA matters for sample and hold circuits but not so much for typical audio, in my experience.

In some of the earlier gear they were used in audio paths in preference to electrolytic can types but these days low esr electro’s can easily be used in their place. Some clients in getting gear serviced, like vintage Neve for example, want to replace like for like to preserve the authenticity of the original sound - in those instances I do so. Their claim being that Rupert Neve put them there for a reason. For my own preference I get rid of tantalums - there is a subtle difference in sound in some designs changing type to electrolytic - in my mind an improvement.