Ceriatone Forum

   
Firstly I would just like to express my thanks to everyone who has contributed to this forum. I realized when I took on the HRM 50 as my first ever amp build project, that I was in for a serious challenge. I have relied heavily on posts in this forum as I went along and have managed to put together a working amp now that sounds really sweet in clean mode. I couldn’t have done it without you guys so thanks very much.

Having said that, I do have several problems with the build and I have no idea where to even start looking for solutions. I’m hoping that the gurus out there can help me get things sorted out, so here goes.

What I have:
- HRM 50 kit without tubes and trannies.
- Mercury Magnetics drop-in (my ass) upgrades for PT, OT and choke. PT is connected as per the sketch posted by jeffhamula  in "Mercury Magnetics PT Wiring Help" (July 2012)
- 2 x Winged "C" 6L6GC and 3 x 12AX7 tubes
My readings:
   Bias – V4 = 35.1   V5 = 50.4
   PI – 3A = 319.3V
           3B = 314.4V (this is only achieved with the trim pot cranked fully clockwise)
   Pin readings on pre-amp tubes. (OD readings are with OD Trim set to middle and Drive and Level on the front pots cranked all the way up).
      P1   P3   P6   P7   P8   
T1   Clean   203.8   2.13   209.1   .026   2.01
   OD   203.5   2.13   208.8   .025   2.01
T2   Clean   212.7   2.10   214.8   .044   2.10
   OD   212.5   2.10   212.7   .101   2.10
T3   Clean   319.3   65.4   314   42   65.1
   OD   318.7   65.1   313.8   42   65.1   
What the Amp is doing:
1)   There is a bad “earth” buzz across the board at all settings. Sound is not so much a hum as a buzz. Sounds like something that should be grounded isn’t, or something that shouldn’t be grounded is. Have no idea where to even start looking.
2)    The switches in the pre-amp section all seem to do what they should be, but there is no discernible modification of the tone from the Bass, Mid and Treble pots. Regardless of which setting they are at, tone is exactly the same.
3)   The Amp does not overdrive. Nothing; zip; squat. The only way I can even get close to getting the tubes to saturate is to crank the volumes to insane levels. Sounds great but I won’t stay married for long!! All that cranking the Drive and Level pots does is makes the clean sound a lot louder. It’s the same whether using footswitch or not.

Against the schematic, I’ve done a 360, top to bottom check on compliance with schematic, joints, wiring, routing etc., rewired or rerouted anything that looked dodgy and can’t find anything obviously wrong.

That’s it guys. Hope someone can help me with this or I’ll shamefully have to send it back to Nik to fix in defeat.

A couple of obvious questions first

Does your foot pedal work, do the lights turn on and off and are the swithes on the back of the amp set for the pedal?
If the PAB is on the TMB knobs will have no effect!
Does PAB work?
If you swap V4 and V5 does the 50mv reading follow the tube? if so they are not matched and I would suggest getting another pair.
Are your relays installed in the correct position/direction?
If you can post some pics of the amp guts.

Todd

Hiya Todd

Thanks for your time mate, much appreciated.
To business:
- Found a pair of tubes that match so amp now biased to V4 = 34.9mV and V5 to 35.1mV.
- Had no idea that the PAB "on" would bypass the TMB controls. Controls work fine with PAB "off"
- Footswitch works fine but I cant say the same for my brain!! I'm not sure if it's because of the better matched valves or because I'd not read the manual properly  :-[, but I'm now getting some overdrive. Not quite as much as I thought there would be but I only got there late last night so haven't really had time to try and tweak it to get a good understanding of what's there. If its still not enough to suit my heavier tastes, I might start looking for ways to increase the overdrive.
- Relays are installed correctly (I think). Couldn't see from the schematic so hunted through tons of photos on the forum and Ceriatone site till I found a picture showing the orientation. There's a picture attached so if you could confirm, I'd appreciate it.

So, 2 down, 1 to go. I've still got the irritating "earth" buzz on the amp. As you'll see from the state of the wiring on the pictures, I've been "chopsticking" for hours trying to find this noise with no luck. I've sent a lot of pictures but if theres anything more specific you would like to take a look at, please let me know and I'll get them posted.

Gavin

Cool man
I  havent had time to look at the pics yet but when i use my OD on my HRM there are only 2 settings for me
1 clean   both OD and PAB off
2 OD      bothe OD and PAB on

If you engage the OD only, your signal goes through both the TMB tone stack and the HRM stack and to me is useless sounding.

I will let you know if I see any issues with the pics that may cause the noise issues your experiencing. BTW the relays are fine if your footswitch is working correctly

Todd

I take back everything I said about the OD!!! I played around with it last night  and this baby really cooks. I hear you on the PAB and OD but really, there is so much tone to play with in this amp, I'll probably still be finding new settings a year from now. Just got to get rid of this damn buzz. Not sure, but would it be of any help if I posted a sound clip of what it sounds like?

Hey Gavin

I cant find anything jumping out of those pics that would cause the noise issues other than possibly your heater wires being ran somewhat close to some of the pre-amp tube wiring. Maybe try lifting any wires atleast a 1/2 inch away from the heater circuit wires if possible. Also make sure and roll your preamp tubes as well to make sure you dont have a bad or microphonic tube causing the noise.

Let us know if that doesn't do it

Todd

Buzz gone ;D Rolled tubes through, no change. I figured it had to be the wiring so I ripped out the heaters, ran all the signal wires flat on the deck and the heaters over the top. Job done.

Now a question that may already have been answered but I can't find it. To get decent overdrive, I have to crank up the preamp volume to at least half way. If you're using the foot switch, is there any way to get a balance between the clean and overdrive? Obviously when you kick out the OD, with the preamp up, the difference between clean and OD is really loud if the OD level is not turned that high up. I'm just wondering if this is a common thing with these amps or if there may be something wrong with my amp that the preamp volume needs to be up so high to get drive.

Other than that, loving the sound!!!

I have the Bluesmaster which has the seperate masters for clean and OD like the HRM. I normally have the OD master a lil lower than the clean master, especially if i have the HRM bypassed. The OD channel can SEEM louder than the clean due to the increased harmonics, etc. You can try messing with the OD trim as well to get a lil more Drive at lower Preamp volume settings as well. Did you also know there is a "hidden" pull bright on the HRM's OD master volume? You may be able to give that a try and have your Pre volume a lil lower as well.

Gregg

Thanks Greg. Will give it a bash. Its just clearly an amp that doesn't like being played quitely. I'm hooking it up to a WEBER Headphone Tap tonight to get my wife off my back.

Do you have a C-Lator? If not, i would consider getting one. Acts as a Global master volume, and allows you to turn the Masters up on the amp and control the overall volume. Works pretty darn well!

Gregg

Got the Kleinulator and am going through the manual now. Will keep you posted. The WEBER headphone tap works ok but takes away SOOOO much tone. Will keep you posted ;)