Bottlehead Forum
Bottlehead Kits => Mainline => Topic started by: deserat on January 10, 2017, 09:13:40 PM
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Resistence Checks are fine.
Voltage checks that are off:
+275 is 260
kreg is 2.9
Thanks
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Are both Kreg voltages 2.9? Are all other voltages spot on? Were you able to bias the 6C45's properly?
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I'm sorry. In my world (software) I'd consider my post a very poor bug report.
I don't recall the value of the initial voltage check which was done after building the Power Supply Board but I do recall it was in range. Or I'da stopped then.
Resistance checks appear to be fine. Though I was concerned about some resistances until I understood that * meant that the resistance on the given terminal could be anything but zero. I was expecting it to leap around for each terminal based on the wording in the manual. When it occurred to me that many of the terminals with * were attached to nothing and my volt meters ( I used two at this point as I thought there was a mistake ) were reading them as 0.0L. If that is a wrong assumption then my resistances are totally wrong.
+275vDC on the Power Supply Board - reads 255 to 260
+6.3vDC on the Power Supply Board - reads 6.2 to 6.35
IA on the A side C 4 S Board - reads 255 to 260
IA on the B side C 4 S Board - reads 255 to 260
Breg Regulator Board (both sides) - reads 221
-reg Regulator Board (both sides) - reads 0.*
Kreg Regulator Board (both sides) - 2.6 to 3.0
I have not attempted to adjust bias on the tubes... the words "highly regulated" scared me into thinking that a 100% + variation on the kreg was enough to be deeply concerned about it even if it is only 5 Volts.
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Go ahead and bias up those 6C45's, those voltages aren't particularly concerning.
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Thanks. Am out of town for the weekend will get back on Tuesday.
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Alright got the volt meter out tonight.
Biasing the B side of the board let's me adjust voltage up to 265 and down to 240.
Biasing the A side fo the board has no impact.
Biasing the B side impacts both terminal 20 and 30.
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Yeah, there's an issue with the jumpering or construction of one or both of the boards. You'll need to go through each step and check off what you have vs. what's in the manual.
-PB
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By both of the boards which "Both" do you mean? I'm guessing you mean Power Regulator and 6C45P regulator. Not the C4S 's. Just trying to save myself some time and focus on the most likely suspects.
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By "both" boards, I meant both the high current C4S boards and the center C4S/bias board. The PC board over the power transformer does not need to be examined.
-PB
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Excellent. Thank you.
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OK so I walked through all the boards again. The two C4S boards match up. The center board had two mistakes in it. Well 1 mistake twice and 1 soldered jumper lead. I soldered the unattached lead. I want to make sure that the way I plan to solve the other mistake is appropriate.
I managed to skip right over the red text telling me to attach the lead under the screw to the center lead on the trim pots. I'm guessing I can simply clean and trim one of the scrap leads from the build and create the bridge. Is that an appropriate solve or should I find and order new trim pots?
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Went ahead with soldering a spare lead between the Pot leads. Resulted in proper readings off main power supply board. 275 VDC. 6.3 is still 6.3
Breg still 220VDC
-reg still 0
Kreg now 10 VDC
IA on both A and C sides 240 VDC.
Biasing ranges from 240 to 160
B side trim adjustment still affects 20 and 30.
A side trim adjustment still does nothing.
Assuming solution is still RTFM. So back to RTFMing... but communicating progress just in case.
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It looks like you're getting closer. When you said your biasing range of voltages, that is still only on one side?
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Ya. Only one side of the board affects voltage for both 20 and 30. If you can know of particular board or interboard connections I should focus on I'd appreciate it. I only get an hour or so at night to debug at night when I can, which makes focused methodical debugging somewhat difficult.
thanks
-v
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Sometimes it can help to print out the assembly steps in the manual. There are PDF printing options to print two of the manual pages per sheet of paper. As you check each step, you can just mark it off with a pen.
The other option is to send your Mainline in for a flat rate repair. Having repaired a few Mainlines myself, I can say that my debugging process for figuring out what was going on in each case was to just work through the manual until I found the improper connection(s).
-PB
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OK the A board had the red jumper run from IA to OB.
+275vDC on the Power Supply Board - reads 285
+6.3vDC on the Power Supply Board - reads 6.29
IA on the A side C 4 S Board - reads 220
IA on the B side C 4 S Board - reads 220
Breg Regulator Board (both sides) - reads 220
-reg Regulator Board (both sides) - reads 0.*
Kreg Regulator Board A side - 2.9 B side - 6
B Side regulator now biases post 20 to 145
A Side regulator still has no impact. post 30 consistantly reads 220
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Well, I'm glad you found the culprit.
To get things more narrowed down now, I would recommend swapping the big PC boards to see if the voltage at terminal 30 becomes adjustable with the C4S board from the other side.
This will determine whether the miswired jumper has damaged the C4S board (this would be indicated by being able to adjust the voltage at T-30 after you do this swap), or if there is still an issue on the center C4S board preventing biasing (indicated by T-30 still sitting at 220V after you swap the C4S boards).
In either case, you're getting a lot closer to having a working amp, keep at it!
-PB
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Thanks. Should be able to do that tomorrow night.
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Swapped the boards twice and labled them so I didn't get 'em mixed up. 30 still doesn't bias. 20 still does.
Does this indicate it's the central board? Or is there some chance that I mis-wired or the tube? The tube does light up.
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Yes, there's still an issue on the center board, or potentially a very hard to spot miswire in the amp. Be careful of the unused pins on the 9 pin socket on the offending side.
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Staring at the center board everything looks to be in the right place. Two things I'm noting.
the 2N2222A transistor on the B side of the board looks a little blacked, like burnt. I don't recall seeing any smoke but, hey I thought I had the thing wired correctly.
Any chance you could link me to the right transistor over on digi-key or mouser? While I'm at it I think replacing the trim pots that I over snipped the leads on might make sense, may as well get it right.
I'm guessing the trim pot is one of the 2K variants of these but I don't know which:
http://www.digikey.com/products/en?keywords=%202N2222A%20transistor
Same thing here for the 2N2222A:
http://www.digikey.com/products/en?keywords=%202N2222A%20transistor
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The central 2N2222 is a fine choice. You might want to ask replacement parts about getting parts directly from us, as there will be less guess work.
An acceptable substitute for the trim pot is Digikey 3299Y-202LF-ND.
-PB
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Thanks I'm email replacementparts now.
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Ok. Got parts. Put them in... no affect. It's gotten to the point where I've taken the c4s boards off so many times that the hookup wire is breaking. Given that there appears to be no way to debug the amp beyond the stated few voltage checks, I'm throwing in the towel and will take advantage of the repair service. Thanks for ya'lls help. It has been that kind of frustration that I consider fun.