BHK 250 fuse issue

This afternoon I replaced the SR Orange fuses in my BHK 250 for the transformer output (10 amp fuse) and the tube power supply (2 amp fuse). Result: no music. I can see the red lights around the tubes lit, so I think the 2 amp fuse is OK. When I put my hand on the heatsinks, after an hour, they are at room temperature. This suggests that the 10 amp fuse is bad. Tomorrow morning, I will put the Orange fuse back, which should confirm. Of course, I’ve double checked all the connections.

However, I am wondering why the amp appears to work normally if there is a bad fuse. There are no thumps or clicks when I turn the main switch back on. When I bring it out of standby, the front button flashes for 30 or 40 seconds as usual and then goes to solid blue. I believe that the 250 does some kind of self-check on start up; would this not spot a bad fuse?

I suggest you read the manual of your product:

Are you using an H-rated fuse? (It’s not the same as a Class H fuse).

Yes, I’ve read the manual and I am aware of the H-fuse issue. I took a chance using the SR Orange fuses and had no problem. I’ve read that some other BHK 250 owners have done the same. (SR fuses do not come in H rated versions – I inquired about this a while back.) If necessary, I can put back the stock fuse which should be H rated.

But I still wonder why the amp appears to be working properly with a blown fuse, assuming that’s the problem. Once or twice over my audiophile career I have experienced blown fuses. The components have always shut down completely, with no lights or anything.

So have you put the supplied H-rated 10A fuse and 2A fuse back in and does it work?

My advice is to get a multimeter and test the fuses. I removed all SR Orange fuses from my BHK 300’s because they were failing on in rush. I blew two and had enough and moved on to another brand. Chris at VH Audio made this good but really they are grossly out of spec and fail under normal use.

Thanks, I’ll see if I can borrow a multimeter. I guess I got lucky with the Orange fuse in my BHK 250, so I figured the SR fuses were OK in this amp and tried the Purple.

That’s what the H-rated specification is designed for: a high current when you turn the thing on. It’s nothing to do with the brand and @watchdog507 fuses did not fail under normal use, they were the wrong fuses in the first place.

For the record I have been using 2 SR Purple (AC input) and 4 SR Reds (high voltage PS rails) fuses in my BHK 250 for months without issues. Of course YMMV.

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I got ahold of a multimeter but its batteries are dead (of course). I’ll have batteries by tomorrow and will be able to test the fuses.

As usual from the bully pulpit! The fuse was spec’d correctly according to PS Audio requirements. The dealer who sells large numbers of SR fuses acknowledged that he’s had a multitude of returns with failed SR Orange Fuses. He gladly replaced them with SR Purple. I’ve not had failures with the Purple variety.


Having found what a complete fraud some of the fuse market is, being sold on fake science and $0.30 fuses being rebadged and sold for $10,000, I have only been suggesting people follow the manufacturer’s instructions and use the supplied non-standard fuse. PSA even offer to provide replacements for free.

PSA also advised that they install what are effectively after-market fuses out of the box.

I’m curious if @magister put back the PSA supplied fuses and confirmed that the amplifier is, hopefully, not damaged.

I finally got a hold of a functioning multi meter. (The first one I borrowed didn’t work, even with a change of batteries.) Hopefully tomorrow I will have time to experiment and find out what’s going on.

To recap, since it’s taken me a while to chase this down.

  1. Replaced SR Orange fuses with SR Purple; no music, even though everything looked OK (standby/on button flashed for 30 seconds then went to solid blue as usual, and tubes were lit). Double checked all connections and made sure the DAC and preamp were not muted.

  2. Put the 10 amp SR orange back; same result. ???

  3. I wanted to put the stock 10 amp fuse back but couldn’t find it. I’m sure I kept it but it wasn’t in the drawer with all my other fuses.

Borrowed a multi meter, but it turned out to be non-functional despite a change of batteries. I finally got a functioning meter, tested the Purple, and it passed connectivity with no problem; so it’s not blown.

A couple of days went by when I had no time to mess with the stereo. Yesterday I put the Orange back. Without changing anything else in the system, I had music as soon as I turned on the other components. Today I reinstalled the Purple, and everything works as expected also.

So I am flummoxed. There is no fault with the SR fuses it seems. Maybe the BHK 250 just needed a vacation. Who knows. I’m just glad I won’t have to ship the amp back to Boulder.

After a few hours of burn-in, the sound is clearly improved with the Purples. I will go into greater detail after I have more time on the fuses.

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The only thing that makes any sense is that there had to be an issue with the fuse holder contacts. People spend allot of money on fuses and do not consider the limited contacts of the fuse holder.


Thanks, that’s a better explanation than anything I can think of.

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Did you perform any PSAudio firmware upgrades of any kind without cycling the power on said unit? Whenever a firmware upgrade is performed a power cycle should be done. These units are purpose built computers without typical I/0 devices.

To the best of my knowledge, the BHK250 has no provision for firmware upgrades. There is no USB slot or Internet connection. It’s kind of refreshing, actually, to own an audio product that doesn’t require firmware to function. And, of course, changing a fuse requires that power be completely turned off.


I was referring to other PSA products you may have. Like the pst or Dac or pre. Sometimes when we can’t figure it out it’s simply F.M.