I was very interested in the discussion about a change implemented to the BHK preamp after a warranty repair. My preamp is on it’s way back for DC offset causing popping when shutting down or muting. Where did that discussion go? I wanted to communicate with whomever posted it and I cannot find it to do so.
I don’t know so much that it was a change, or that the technician didn’t fold the component flush to the board. My BHK Pre has that component folded for access to the jumper. The tech must have been unaware of the impact that would have on the jumper.
Is your preamp new production or was the change implemented on a repair?
I started the original thread.
What I’ve learned from PSA is that the boards with the offending cap are outsourced. It seems like the supplier just stopped folding the cap down and no one at PSA seems to be aware of this.
Worse, as James looked at several new and not so new preamps, there seemed to be a lack of uniformity.
If I was buying a new unit or sending mine back for service, I’d specify that they confirm that in it’s completed state, the voltage jumper is unrestricted. Clumsy but there seems to be no other answer.
Ps----@Dirk showed a photo of his where the board just pulls out, making access easy. Well, mine won’t come out because some of the boards are soldered in. And some are not. higgledy piggledy.
Thank you for replying to my post. I was curious what the cause of your preamp needing to be returned for service. My was sounding fine and suddenly started to make a fairly loud pop when I turned it off or muted it. In a way I was glad it had to go in for service as It made a ticking sound with every step of the volume control whenever I tried to use 6 volt tubes in it. I remember seeing someone else have the same issue and BHK replying and saying it had to do with the very boards that are causing the interference with the voltage jumper placement. At least I still have music as I can drive the BHK 250 50 directly with the dac. I have to admit I do miss the preamp though.
Mine just started hissing and making loud popping noises thru both channels.
I was told that my input board warped. Go figure.
Mine also pops very faintly with volume changes. I think that’s probably the tubes but I don’t care about that.
All that said, the thing sounds freakin glorious.
My BHK amplifiers exhibited the same popping noise you described. I returned the preamp to the UK distributor for repair - when it was returned to me my system still banged and popped through the speakers when switching On / Off, Mute operation, etc.
It was the BHK250 input board that was faulty. I was massively overcharged for the fitting of the 250 input board - which PS Audio supplied FOC - hence brought any future dealings with the UK distributor to an end. My preamp developed a loud hiss from the left channel - which was so loud I could hear standing next to the right speaker. Tried new tubes but the preamp was faulty.
Jim Laib arranged that I received new BHK preamp, 300s and a 250! Jim was good to me. I dealt mostly with Jeremy Bretey and he is top notch.
I am confident that the preamp is the cause of the popping. The system is dead quiet when using the dac to drive the amp directly.I can put the dac into standby and mute and restore without any noise at all. The truth will be known when it returns from service.
The pictures Ron had posted looked like the bias board has a different layout than my preamp. Mine look just like the ones pictured in the owner’s manual. I have to agree that whomever is producing those boards needs to be consistant with the positioning of the components. The different layout of the boards looks like a running desing change to me.
It’s more than likely all current production preamps have removable boards so the orientation on the blue capacitor is irrelevant. The problem arises when the new board with revised layout is installed in earlier model preamps where the board isn’t removable. This should have been discovered before installing them into earlier models like Ron’s preamp.
There is a similar issue with BHK300 input boards. But that is another topic for discussion !!!
My unit would be one of the older ones as It was purchased new in August of 2017. Maybe with all the focus on this they will make sure they do not interfere with the voltage strap should they need to replace my boards.
Ron, this image is from my Owner’s Reference. It looks exactly like the Bias Boards that are currently in my Preamp. If you compare it to your picture you can see the board layout has change significantly.
It appears that the cap is black and bent downwards in the image. So a revision of components. That’s understandable over time. I don’t change my voltage often as I’m happy with my Telefunken 6DJ8’s. But if I went to 12 and back to 6 often it would annoy me.
Your eyes are better than mine. I did not notice the Black cap. I wish Ron’s pictures were still up so I could study them better. It may be as you say just a change of cap. Thanks for spotting that.
@sixpack1 - yeah - looks like a black cap right behind the stakes and it does not seem to interfere like Ron’s board…
Is that not a black IC and the blue cap is below the IC lying flush with the board.? Looking at the photo of Watchdog507’s BHK preamp layout on the “BHK PRE Running design change” thread…
Even though no reply from on high, there MUST be SOMEONE who gets paid for production or QC who can easily see that this new config eliminates or makes unnecessarily difficult switching voltages (going to or from 6/7 volt to 12 volt tubes.) It’s a puzzlement!
I love the King and I. i appreciate your omage with the it’s a puzzlement comment!
So, we figured it out. We started soldering the boards down because before when they were clamped, they were coming a little loose in shipping. With them being soldered, they sit a little lower like a low rider truck. For those that are being soldered, the caps should be bent down so it’s vertical. Ron, feel free to give me call later today and we can check out your pre amp. Thanks!