Hello all,

Ok, time to swallow my pride and ask for some help. Just finished building and firing up new HRM 50. After making sure nothing smoked using a dummy load. I plugged in a speaker and turned it on and first thing was squealing due to OT primaries backwards. I emailed Nik about this becuase the layout and photos show opposite wiring. He said go with layout but that is wrong.  So I reversed and the squealing stopped but I'm left with a crazy loud hum, like something is very shorted to ground or wired backwards. Along with this there is absolutely no input signal getting to the speaker.

I'm a bit frustrated right now, because I took my time building and have been going over it with a DMM, scope, and my eye checking my wiring, and can't figure it out. 

I'm throwing this out there right now, even though I haven't taken any photos and haven't gotten key voltages yet in hopes that is might jog somebody's expertise and point me in a direction. The wife is sleeping right now and the hum is so loud that I can't mess with it much more tonight without bugging her. I will get some photos and voltage check tomorrow.

Any help will sure be appreciated. Thanks.

Just to verify, you're saying you heard that these Ceriatone OTS output xfrms 2ndary have been wired backwards?

It's after midnight here on eastcoast so I'm going to call it a night, but thanks for the quick return. Tomorrow i'm going to dig in and get measurements written down. I have a bad habit of taking data and not writing it down thinking I'll remember. I know better. I'm too old for that crap.

Plus, start looking for bad connections. I've been reading about tightening down the relay & rectifier boards too much and causing problems. I may have gotten over zealous. Although I do remember all the HT voltages seemed OK.

Anyway thanks...c'ya tomorrow.

Here are some images of the build.

I hesitate to post these voltages because they're obviously whacked, but here it is.

One thing that seems rather important is that I'm measuring 380Vdc to ground on the shield/ground of the speaker output. It's just there and not on the chassis. Thank God. So it seems to me that something is wired incorrectly, but I can't find any faults in my wiring compared to the layout. I still have some things I want to check. What's the best way to test the OT for proper wiring?
 
         Pin1  Pin3  Pin4  Pin5  Pin6    Pin7    Pin8
V1    4.15  .041           .050         -.632
V2    421    360             0             .004
V3    422    340             0             298
V4    37mv  481   480  -49.3  479             36mv
V4    37mv  481   480  -49.3  479             39mv

OT CT=480
 

Something around your speaker wiring is way wrong - the sleeve of these jacks should connect to ground, and hence the chassis.

Also, if you look at the 22uf filter cap on the tagboard on the wall near V1 your will see that I mixed up the 2.2k and 220k resistors. Nik found this mistake lastnight.

Ok, back to work and hopefully playing soon.

Thanks

Yippy, It's alive....(in the voice of dr. frankenstein)

Man ol man, this thing sound great and I haven't even got it totally setup yet, just biased. (using old tubes, and have HRM & PI set at 12:00). Basically, I just plugged in a guitar to try it out and ended up playing for about over an hour.

Thanks again to all that have helped, including sduck, that was on the right trail.

I have some question about voltages, but I'm going to start a new thread and put this to rest.

Just bend the wires, it's the EMI from the heater wires that causes a degenerating tone.

Voltages are a bit high but that could also be your wallpower; when 120 is 125v, you get these voltages on the tube side(like in your chart).

Believe it or not they arrived today. Mine were sent on 2/28/11. I had given up on them. So yours were sent just a few days ago. I thought we were talking about this before that? Anyway, USPS from Maylasia is very slow. So I learned a lesson....if in a hurry use UPS and not USPS. 

Yes, the best lessons are from mistakes and troubleshooting. I wanted to get to know this amp in and out anyways. Just with a bit less stress. And really the only stessful thing was being concerned about destroying a few hundred dollars worth of components. If money wasn't an issue, I would have been less stessed.

I would like to do another build soon and source my own parts. Maybe something with a bit lower part count. But first things first, I have a bunch of tweaking to do on this amp. I pretty sure this will become my go to amp.

I had jobs on the road all day today, so I didn't get to play at all yet. I think I'm going to put in the new tubes tonight and get a bit more familiar with it. I can tell right off one thing that is so nice about these amps. They're very dynamic, but compress just the right amount when needed. I was concerned when I would read comments about them being "harder to play" or more likely to "show your flaws". But, I think it's going to suit my playing just fine.