BHK 250 Overheating


#1

Just fired up my system like I always do on Saturday morning. Only 1/2 a CD in: music goes off and I see the power switch light flashing on the amp. Touch the top of the amp and almost burn my hand. It was really hot!! I shut off the power and am letting it cool down. Any ideas? I’m a little concerned about starting it up again. There was no obvious reason for the amp to get that hot.


#2

Hello! I’ve experienced this issue with my BHK 250. Two questions, how old is your amp and did you change your speakers recently?


#3

Think I’ve had the amp for 8 months or so. Same speakers I’ve always used with the amp.

just looked it up: I bought it 3 Mar 16. Serial number WA-A2-6C0212.

Well, she’s cooled off for a little over 30 minutes. Going to fire it back up. Hope it was some kind of fluke but…

crap! There’s some kind of fault with the amp. The load on my P10 is at 30% with the amp in standby and over 50% when on. That’s never been the case. More like 25% maximum.


#4

My BHK 250 is a beta unit from May 2015. But, my experience overlaps yours. From May 2015 until February 2016 it worked flawlessly with my B&W 804D2 speakers. At the end of Februay I downgraded, big mistake, to Paradigm Prestige 85Fs speakers. Within 2 hours I had the same experience you did, amp overheated, went into protection mode, and the front light flashed. I let it cool down, checked all my connections and tried again. Same result. After switching out amps, cables and speakers, the problem was isolated to the BHK. I shipped it back to PS Audio at the beginning of March 2016. I did not get it back until April 2016 because PS Audio had to identify the problem, develop a fix and test it including listen tests. Paul mentioned the fix was related to high frequencies over 180k hz and would be applied in production. My advice, contact PS Audio either Customer Support or Paul.

Please note, a month repair sounds like a long time. In this case, having worked for a German car company for 20 years, its was pretty impressive. To their credit PSA had to identified the problem, developed counter measures and completed testing, and did so in less than 30 days.


#5

Thanks for the response. It’s a first world problem but I sure am bummed. Can’t deal with the issue for a while. I’ll be out of the country for a week. Life without music in the house is just not the same. Plus, not looking forward to shipping this beast!


#6

I hear you! I hate sending equipment in and/or being without music. I did discover an in term solution I deployed for a week or so while I isolated the problem. If you change your DS DAC output setting from high to low, it kept my BHK 250 cooler and it did not shut down. It does require a high volume setting though. Good luck!


#7

Just tried the only troubleshooting I can think of, besides checking connections, and replaced the tubes. That wasn’t the fix. The load on my P10 is bouncing from 50% to 75%. That has never been the case. I’ll reach out to PS Audio tech support in a week or so.sad_gif


#8

Little more sleuthing using the P10 for data. The normal load on the BHK 250 in standby is around 100 watts. Now I’m getting in excess of 250 watts just in standby. Don’t know when the jump occurred but I assume sometime between Thursday and today. Thursday was the last time I had the amp on. We did have a short power outage on Friday. Don’t know if that caused the problem. Certainly not the only power outage we’ve had over the last year or anything that unusual.


#9
amsco15 said

Just fired up my system like I always do on Saturday morning. Only 1/2 a CD in: music goes off and I see the power switch light flashing on the amp. Touch the top of the amp and almost burn my hand. It was really hot!! I shut off the power and am letting it cool down. Any ideas? I’m a little concerned about starting it up again. There was no obvious reason for the amp to get that hot.


I had loaned the original prototype 250 amp to a friend. After some months of use, the amp started to go into protect mode. Before it did, one channel was quite a bit hotter than the other one. I disassembled the bad module and took it home to work on it. Turns out that one of the input MOSFET devices had become leaky - meaning that it conducted more current than it should. Replacing that device fixed the problem. So, in your case, I would fire it up and see if one channel gets noticeably hotter than the other. If so, that might the problem.

Another thing that has happened is that an amp goes into high frequency oscillation because of a particular load and overheats. If one disconnects the load and the amp then remains at the normal temperature, that could be the problem. That did occur in some amps in the beginning and we fixed that by changing the high frequency stability compensation network.


#10

Thanks for responding Bascom. My bet is the leaky input MOSFET. I’m pretty sure the left channel is the trouble. Don’t know if it’s related but I’ve been noticing more noise and hum from the left channel over the past few weeks and now the big problem. Also, the left side of the amp, as you face the front, was the super hot side.

My speakers have been exactly the same since I bought the BHK 250. I’m sure this doesn’t eliminate the possibility of the high frequency problem, just seems unlikely that it would manifest after a year. Looks like a trip home for the amp is necessay. I’ll miss it while it’s gone!!

Thanks again.


#11

Not sure if my experience is relevant, but I sent my beta BHK250 in to have the binding posts replaced (as recommended by Paul). The amp was sounding fine and I did not have any overheating issues. Interestingly, I have been using Goertz speaker cables which do send some transistor amps into high frequency oscillation. Bascom assured me that would not be an issue and I have no specific reason to think it was, but his comment makes me wonder. What suprised me when I found out what was repaired on my amp, is I had a couple of “failed” items that weren’t sonically noticeable to me. Here’s what the tech said (I’m not shouting here, I just copied and pasted from the e-mail):

OUTPUT BOARD FAILED ON LEFT SIDE, REPLACED WITH NEW ONE.
TRANSFORMER FAILED FOR HIGH THD, REPLACED WITH NEW ONE.
ADDED GROUNDING BLOCK BOARD, AND REPLACED ALL 8 OF OLDER VERSION BINDING POST.
RE-FST AND RTC HQ8, THIS UNIT GOT UPGRADED TO PWA-A8-5E00xx

Not sure of the significance of the first two items, but the amp sounds as good as ever so hopefully it doesn’t matter. I just hope neither is connected to high frequency oscillation.

One thing I should add is the time to repair my amp was about a month (plus shipping time). In defense of PS Audio, I think my timing was real bad, the Stellar series was just beginning production so everyone at PS Audio was very busy. If you are thinking of sending your amp in you might want to inquire about how busy they are to make sure you can tolerate the “separation” from your amp! Luckily I had a spare so I was ok, just not in sonic bliss …


#12
pmotz said

(I’m not shouting here, I just copied and pasted from the e-mail)


:slight_smile:

#13

pmotz,

Do you know the series on your amp before you sent it in? A1 or A2? I just got an RMA from PSA to send my amp in. I’m out of the country for a week and can’t send it in till I get back. Making me nuts. I love my stereo!

I have had some 60hz hum issues with the amp from day one. Had to pull the ground plug to make it stop. Hoping updates will solve that problem too.

Thanks all. I love that PSA allows this site to exist and freely discuss even when there are some warts! Love the feedback and support!


#14

For what it’s worth, my overheating 250 had the ossolation issue BHK mentioned. S/N: PWA-A1-5D0010


#15

Amsco15, my amp was the A1 series. A8 is apparently several iterations along the evolutionary path. Very interesting …

norton, do you know if the oscillation issue was caused by an internal fault, or an external (i.e., odd load) fault?


#16

Back in the USA and just shipped my BHK 250 to Boulder. I’ll miss her while she’s gone but great to know PS Audio will take care of the issue for the cost of me shipping the amp to Boulder. Nice service!


#17

Hello pmotz, my oscillation issue was diagnosed as being caused by speaker load. Their fix was a change to the amplifier’s high frequency filtering from -3 db down at 200k hz to -3 db down at 180k hz. Best, norton


#18

I’m sitting in my office anticipating the arrival of the FedEx truck, I have an office by the window next to the parking lot and front door. I hear the truck and before I can get out there, he’s dragging my beautiful BHK 250 down the steps of the truck one at a time. pulling-hair_gif I quickly dead-lifted the beast up (think I lift weights so I can handle this amplifier) and put it into my car. I’m sure everything will be fine, can’t help but wonder how often these 93lb beasts get beat up in shipping.

It’s going to be a short afternoon in the office. Won’t make it much past 2:30. Need to head home and set my baby back up. I have a new Cary SLP-05 pre-amp and refurbished BHK 250 to take for a spin tonight. Might be some Whistle Pig Rye Whiskey involved at some point too.


#19

My BHK250 arrived at noon today. After about 8 hours of playing music at low volume for burn-in, I decided to rearrange a few of my components and was shocked at how hot the amp felt. It was too hot to touch for more than 3 seconds. This cannot be normal operating temp! Anyway, I searched this forum and found this thread. Based on the information here, I might have a problem amp. My serial number is PWA-A1-510118

I purchased it new directly from Amazon for a substantial discount from MSRP. I’m not feeling good about this. Seems like I might have an “old new stock” version, based on the serial number. And not to derail this thread, there’s also loud hiss coming out of my speakers. I unplugged everything, except speakers and the noise was still there. I’m plugged into a PS Audio Duet. My McIntosh MA 5200 with all other gear connected is dead silent.

Should I return it as defective to avoid ending up with a lemon? I am not spending a penny to ship it to Colorado for warranty repair. It hasn’t even been 24 hours. With all due respect, maybe I should stick with McIntosh.


#20

I too had purchased the 250 from Amazon a while back (also A1 series) and it does get hot when under load but that seemed about right to me based on all the reviews, and comments here. It gets hot to the point that I cannot hold my hand on the sinks for more than 5-6 seconds. The front, top etc… are reasonably warm but not hot at all. Under stand-by its definitely cooler and i can hold hands indefinitely. For what its worth I have mine in an closed-sides cabinet but I keep the front ventilated plus I have whisper quiet suction cooling behind the amp. The fans are thermally controlled and I have a monitoring thermocoupler at 1 inch above the heat sink and measures about 98-104 F when the amp is hot and the cooling does its job. That means that the fins are prob closer to 110-120F or so. As long as you allow adequate ventilation I think it should not be an issue but I’d like to hear others’ experiences too.