Hi all, please forgive me once again for my noobiness, I just want what's best for my audio interface 
. Mostly I'm trying to mitigate overheating.
Several posts have indicated that a change to LDO regulators would be beneficial to this PSU, but there's conflicting advice.
Also, it looks like many change the four in4001 diodes at the top (D1-D4) to schottky type. Question: since many people seem to automatically change all PSU diodes to schottky types, why not change D5 and D12 as well?
Can anyone confirm or dispute these recommendations? Thank you!
. Mostly I'm trying to mitigate overheating. Several posts have indicated that a change to LDO regulators would be beneficial to this PSU, but there's conflicting advice.
Also, it looks like many change the four in4001 diodes at the top (D1-D4) to schottky type. Question: since many people seem to automatically change all PSU diodes to schottky types, why not change D5 and D12 as well?
Can anyone confirm or dispute these recommendations? Thank you!
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Shottkys might give a slight efficiency advantage due to slightly lower forward junction voltage.
For a 9vac input and given the 470uf coupling cap values, the current that can be drawn is very limited before it would start to impinge on the 78xx regs drop out voltage. Anything much over 100ma will cause problems. Unless the current is way below that figure then increasing the 470uf to say 1000uf would be the (my) first thought.
Without knowing the actual current draw on each rail its hard to say... it could all be fine, or it could be very marginal.
For a 9vac input and given the 470uf coupling cap values, the current that can be drawn is very limited before it would start to impinge on the 78xx regs drop out voltage. Anything much over 100ma will cause problems. Unless the current is way below that figure then increasing the 470uf to say 1000uf would be the (my) first thought.
Without knowing the actual current draw on each rail its hard to say... it could all be fine, or it could be very marginal.
This is a reason to switch to LDO's (LM2990T and LM2940CT), right?
Not enough space for that.. in fact all of these cap values are appear to be maxed out in terms of space.
Not for over a second.. They're around 100C I'd say. Here is the advice I'm going by... is it good or no?
"I used to build industrial control equipment and one of my pet hates is under engineered power supplies in audio gear. You could get a big improvement just by replacing the +/- 15V regulators with low dropout types like the LM2940CT-15 and LM2990T-15. Also replace the rectifier diodes (the four 1N4001s next to each other near the 9Vac input connector) with Schottky types like the MBR1100, for a lower voltage drop. You'll get a cleaner supply without the extra heat that bigger booster caps would cause."
New good quality caps shouldn't get hot. You need to check whether it really is the cap heating on its own or whether it is heat from the regs affecting the cap.
Also measure the 'DC' voltage across them and check they are fitted correctly as per measured results, not board markings.
Without context ("I am trying to fix specific problem X") and some analysis ("Does this actually fix the root cause specific problem?" and "How do I validate that the problem is fixed?"), any advice is suspect. Audio hobbyists frequently latch onto their pet idee fixee and try to shoehorn everything into it; the "tell" here is "one of my pet hates is..."
Mooly's direction is sound- first, try to determine WHY you have this heat before settling on a way to fix it. There's about a zillion Delta 1010s out there and they're not failing left and right, so if that's happening to you, first determine why rather than deciding that there's a fundamental flaw in the design.
As a side note, if you can touch them for a second without burning yourself, they're probably about 60 degrees.
Actually these units are pretty much all failing left and right... Blown caps and overheating is a very common problem with the 1010. As jan.didden mentioned, C14 and C17 are the first to go but a lot of the other caps tend to fail too.
I should have clarified but I really meant "only for a fraction of a second." I used to run a 100C hot plate all the time in my lab and had touch it with my bare hands daily. It's around that temperature (maybe closer to 80-90C), and that's just from being on for 5 minutes. I haven't felt them under actual use.
It's a well-known issue. But I'm not just trying to get it into working order, I want to extend the life of the electrolytics as much as possible, so I can close it up and forget about the whole thing for the next ten years or so.
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Right, at first all the caps were way under spec and they were popping by just looking at them crooked. After getting too many returns maudio replaced them with the values you see on the schematic, but they still overheat and blow (as happened in mine). As I said, they can't really go to bigger values due to size limitations. I changed everything to panasonic FC/FM at the same values and it's pretty cramped.
The diodes tested fine but consensus seems to be to switch to Schottkys.
I guess my main question at this point is whether switching to LDO regulators for the 15V rails would benefit the heat situation. I've seen a few mentions of switching to LDO's and I've also seen mention of moving the regulators off of the board entirely.
I basically can't find definitive advice like this on whether swapping with LDO regulators will help. Asking another way: could they hurt?
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