Space Heater - simple tube preamp
- Thread starter vigilante398
- Start date
only if a Cranberry...
Mike McLane
Active member
Just finishing wiring up my SH. Is there a proper orientation required for the IRF740? I don't see any indication on the PCB.
vigilante398
Authorized Vendor
Yes, there should be a line on the PCB that shows which way the heatsink goes.
Mike McLane
Active member
You mean the line that's on the opposite side of where I have it installed????? 
MichaelW
Well-known member
I had the same question, didn't see the line, I just looked at @vigilante398's build pictures and copied the orientation......makes me look smart but I'm just a monkey....hahahaYou mean the line that's on the opposite side of where I have it installed?????
Caldo71
Active member
I got this right the first time by pure guesswork and deduction just cuz the lines silkscreened on the PCB seemed to show a “fat” side and a “thin” side to the plastic sammich around the metal plate.
How long has the retail Black Eye II been available?
vigilante398
Authorized Vendor
It's a new release for November 2022, so it's been available as a pre-order custom build for about 2 weeks.
Mike McLane
Active member
Got things rectified (amplifier joke??) with the IRF740 and when the GAIN is turned up a little over half way I get a "warble" (sounds like R2D2 from Star Wars) followed by a high pitched screeching the rest of the way up. Its roughly a high frequency multiple of 60 hz cause it is enharmonic with the B on my guitar. Tried two different JJ tubes. No problems on the LEVEL. Got any recommendations?
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vigilante398
Authorized Vendor
Can we see a picture of the build? What kind of tube do you have in it?
Mike McLane
Active member
JJECC83S tube. Pics attached. I scrubbed everything down with alcohol when done. I was using an exacto knife to be sure there wasn't any "spill over" on the solder joint adjacent to the bottom terminal of the IRF740. It scratched the brown surface of the PCB and it appears that there is copper underneath. Could I have messed something up there?
Attachments
Mike McLane
Active member
I was going to use an ohm meter to see if any of the solder joints bridged. Some "register", but that may be due to their placement in the circuit so I started to note them on a photo of the PCB from the BOM only to notice that the BOM layout appears different than the PCB I have. VIG, am I crazy?? (don't answer that). . . .
vigilante398
Authorized Vendor
You're not crazy, you have the newer version of the PCB which has the LED mounted under the tube socket. Updating the build doc with current pics has been on my to-do list for a while now. It will get done eventually.
I don't think you messed anything up scratching through to the copper ground pour, so I don't really have a solid answer.
I would check your Resistor values are Correct?
Here is a Resistor Calculator, Click on Bands for 5 colours.:
Resistor Calculator
Resistor Calculator is an App developed by CherryJourney to help the user find the value of a resistor.
These look Suspect, the one next to Out looks Iffy???
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MichaelW
Well-known member
The solder pads are pretty tight on this one. You're solder joint game needs to be super on point, just enough solder to get a good bond but not too much or you'll get a bridge, it took me 2 boards to get my first working pedal. The the spots Phil has pointed out in red are definitely suspect.I would check your Resistor values are Correct?
Here is a Resistor Calculator, Click on Bands for 5 colours.:
Check your Solder Joints, this one doesn't look right circled in Red:Resistor Calculator
Resistor Calculator is an App developed by CherryJourney to help the user find the value of a resistor.resistor.cherryjourney.pt
View attachment 35663
These look Suspect, the one next to Out looks Iffy???
View attachment 35666
Mike McLane
Active member
Gonna just start over. The cost of the PCB and the light component count make it less of a hassle. Thx all!!
MichaelW
Well-known member
Been there done that.....twice hahahaha
Mike McLane
Active member
I have rebuilt my Space Heater starting with a new board. After soldering and cleaning I examined the board for possible solder bridges and I once again hit upon this guy and sure enough get continuity across the solder joints. . . .
I could swear that the two solder joints are not touching, but the meter says "yes". The schematic contained in the BOM is the old one and does not correspond to this layout, but from what I can deduce from the old schematic this could be the first stage plate resistor which is separate from the 220K further down the line by the 100n coupling cap which should prevent this "connection" from happening by design shouldn't it? And if this is the 220K contained in the PS then it DEFINITELY should not be happening. Nathan, can you please verify.
I could swear that the two solder joints are not touching, but the meter says "yes". The schematic contained in the BOM is the old one and does not correspond to this layout, but from what I can deduce from the old schematic this could be the first stage plate resistor which is separate from the 220K further down the line by the 100n coupling cap which should prevent this "connection" from happening by design shouldn't it? And if this is the 220K contained in the PS then it DEFINITELY should not be happening. Nathan, can you please verify.
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