Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Reduction => Topic started by: DustDoggy on May 22, 2022, 04:27:48 PM
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So I completed my reduction last week and everything went great so today I thought I would install the integration upgrade. Installed the shunt regulator board and went to check the voltage but noticed the 4 LEDs didn't light up and one LED on each tube socket didn't light either so I turned it off. After checking over my work I noticed my Integration manual has the red wire that is to be disconnected from 4L connected to 57L. My red wire that was disconnected from 4L is attached to 56L. When checking back to my reduction manual it says that 56L is the correct position for it.
I'm not sure these two problems are related but before I go reflowing all the joints I thought I would post here first. Thanks!
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56 and 57 are wired together, so there isn't technically an issue with this.
In order to actually debug what's going on, you would need to perform the voltage checks on page 17 and let us know what is correct and what isn't correct.
If you have one LED on one of the 6922 sockets that isn't lighting up, but the other three are lighting up, then you almost certainly have an issue with the underlying build that needs to be addressed first. I fix a LOT of Reductions with the repair service and I think I have maybe seen one with actual mistakes made, whereas the rest were just poor solder joints that didn't capture all of the connections on a given terminal. This is extremely common on the ground buss wires that run from the input RCA jacks around the 9 pin sockets and into the terminal strips. Pretty much every Reduction I have repaired has a loose wire on pin 9 of at least one of the 9 pin sockets, and this is definitely something that will cause one LED to not light up.
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Thanks Paul! Some reflowing in the suggested areas seemed to do the trick. I just finished the final voltage check and terminal 2 seems a bit high at 101 VDC. All others are within the specified range. Anything to be concerned about?
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Are both the LEDs glowing on the 9 pin socket on that side?
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Yup they both are.
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I would reflow the center leg of each MJE-350 on the C4S board on that side.
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I reflowed the center legs on the MJE-350 and the voltage remained the same.
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Does that voltage follow a tube if you swap them between sides?
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I switched the tubes around and it read the same however I noticed that if i wiggle the power cord around in the IEC power inlet the voltage drops on terminal 2 to 94 DCV.
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Did the chop stick test on all the connections on or near the IEC inlet and the voltage remains the same. It seems only wiggling the cord itself produces the voltage change. Swapped in the cord from my stereomour and the same voltage change happens with that cord.
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It can't be the incoming AC voltage, but you definitely have a loose connection that is being move when you wiggle the cord.
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So I finally had some time to sit down and resolder some joints today. The power cord issue is now fixed. I am still getting 105 VDC on terminal 2. It now looks like im getting 105 VDC on terminals 18 and 26 aswell. Terminal 31 is slightly lower at 102 VDC. Anywhere else I should focus my efforts?
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Can you post some build pics?
Cold solder joints at the center leg of the MJE350 transistors can also cause issues like these, though I would tend to expect dim or completely dark socket LEDs in that case.
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Here are some pics. I also noticed the two LEDs on the A side of the board on the A socket side take a while to light up.
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One black wire on one of the ground post solder lugs looks loose.
If your soldering iron can be turned up higher, I would definitely do that!
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cranked up the hakko and resoldered it. No luck so far.
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I should also note the LEDs on the A socket side board dont' glow as bright as the B side socket board.
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If you have a Hakko 888, it's very, very easy to think you're turning it up but actually to be adjusting the calibration of the iron and making the tip cooler (don't ask me how I know!).
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I made sure to google search the correct way because I heard it's easy to mess it up. It's definitly at max temp.
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Are the tubes themselves still glowing?
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Yup they are glowing.
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Can you very carefully measure the DC voltages at pins 3 and 8 on each 9 pin socket?
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Pins 3 and 8 measure 1.54 DCV on both sockets.
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How about the DC voltages at 33 and 37?
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33 is at 5.86 DCV, 37 is 6 DCV.
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At this point it would be worth trying a different set of tubes just to be absolutely sure of what's going on.
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I will have to order some up. Would like to maybe avoid ebay but it seems the cheapest ones are sold there. Would some new tubes like these be worth ordering? https://www.thetubestore.com/electro-harmonix-6922-gold?quantity=2&additional_options=3
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I'd go for some old stock tubes, maybe something like this:
https://www.ebay.com/itm/265339152996?hash=item3dc7722a64:g:SPQAAOSw7hZhVzK9 (https://www.ebay.com/itm/265339152996?hash=item3dc7722a64:g:SPQAAOSw7hZhVzK9)
If you want to go with a dealer, I'd try here:
https://vacuumtubesinc.com/index.php/6922-e88cc.html (https://vacuumtubesinc.com/index.php/6922-e88cc.html)
If you buy two and ask for a pair, I suspect he would send a matched pair.
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Cool will order some up and report back when I get em. Thanks Paul!
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Just got the tubes in the post today and did the voltage check. All voltages are now well within spec and my system is sounding amazing. Thanks for all the help Paul!