Bottlehead Forum
Bottlehead Kits => BeePre => Topic started by: denteom on December 10, 2022, 10:39:59 AM
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I've completed the build up to the resistors connecting on the coarse rotary switch. When I checked the resistance from Q10 to Terminal (1) I got a correct value of 5K ohm. But testing Q10 to (7) Terminal I got a 0 Kohm value. Not sure how to correct this problem. As of my last checking, I think I don't have a cold soldered joint. Where do start to trouble shoot?
Dennis
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I would very, very, very strongly suggest posting photos of your wiring before attempting any reflowing of solder joints or anything like that. A problem like this is either a miswire that needs to be corrected or a measuring issue with the meter (unlikely since you got the correct measurement on one side).
It's completely possible that there's an issue with one side of the fine attenuator that's actually causing this problem.
If you attempt to reflow your solder joints to get this issue to go away, more than likely you'll melt one of the attenuator switches.
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Hope these photos help
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Are you getting 0K or are you getting OL on your meter?
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Hi What you mean by Ok or OL?
My multi- tester is still an analog meter, I just see the needle move to a corresponding value, which is I set to the Ohmeter multiplier either times 1, times 100, times 1000, amplifying it to get a more accurate reading. The old analog meters once switch to ohmeter need to be zeroed each time. When I tested Terminal one it went up to 5 kohm. But when I checked Terminal 7 it was closer to 0.
When I reviewed the photos I took I noticed that the white wire connected to the lower lug between 7 and 8 has kinda some abrasions on it. I think that was caused by yanking it out from the old volume control? If the wire is damaged from inside can that cause the problem as well?
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The OL vs 0K is a common issue people have with digital meters.
Having 0 ohms on an analog meter means that something is touching which shouldn't be, so not a broken wire unless the wire has broken and is resting against the chassis.
Is the solder on Q7 touching the nut for the switch by chance? If it is, you could side cutters to just trim away a little solder so they aren't touching any longer.
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Having a hard time finding the short circuit issue. I trimmed most of the protruding wire, but still the same problem. Used a magnifying glass to see if Terminal 7 was in anyway touching the screw beside it and it did not show any part touching it. I measured the lower lug between terminal 7 and terminal 8 which also showed it was also 0. So I thought maybe this was causing it, Tried to remove the wire, but because I crimped it before I had a hard time removing it. I just stopped and will ask a friend with better skills than me to remove it.
Just a quick observation, the lower lug is still stuck but almost out, I measured Terminal 7 again and somehow it became 5 Kohm, it was a sigh of relief. Unfortunately after few minutes I measure Terminal 7 again and it is again at 0. Not really sure what's causing the short. I already turned the aluminum chassis upside down and tapped into it thinking maybe something stuck in between but nothing fell out. Terminal 8 to twelve also looks fine though. Can it be a problem of other terminals?
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What DC resistance do you get at coarse terminal 8?
Does the 0 ohms at terminal 7 change if you change the switch position of the coarse attenuator?
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Haven't tried to turn the knobs of the coarse attenuator. What should I find if ever I turn the knobs?
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The reading on 7 shouldn't change if you turn the knob, but if it does, that could offer an explanation for what's going on as well.
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Hi, What's the best way turning the switch. When it was not fixed to the chassis it was an easy turn, I think because I was turning the underside and not the Stainless steel shaft. Tried using pliers with cloth or rubber wrapped around it, it either it won't budge or it was slipping. Don't want to bite on too hard using the pliers might damage the pristine smoothness of the shaft
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Put a knob on it and use that.
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When I turned the knob to 7 the reading on 7 is 0 while on 8 is 2 kohm. It has not change same when the knob was on 1, reading on 7 is 0 while on 8 is 2 kohm
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Does the DC resistance on 7 change at all with the knob on any other position?
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No it did not change even with different positions
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That terminal pretty much has to be touching the screw or hardware under the screw. You may need to take a tiny flathead jewelers screwdriver to scrape away the short.
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Hi, any thoughts on what to do next?
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So, what to do next? Is there a solution?
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Sorry did not see it was on page 2 of the thread. I will try to see if there are any other points touching it. even with magnifying glasses I could not see it. Maybe peering it the morning light would be better.
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You can unscrew the plate where the attenuator controls mount and space it off the standoffs with a little cardboard so there's no metal contacting the chassis to verify that the 0 ohm problem goes away.
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I unscrewed the nut close to Terminal 7, then sprayed contact cleaner. As you can see there is no contact from terminal 7 and the nut. I still get 0 kohm. So just to be clear you recommend removing the attenuator and add paper in between it? Which Standoff? The one connected to the flat stainless steel plate with rounded ends?
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Unscrew the three screws that hold the plate with the level controls to the three standoffs, lift the plate up so it doesn't touch the chassis plate anymore, then recheck that resistance with the attenuator mounting plate no longer touching the chassis.
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Still the same 0 kohm I removed the screws from the standoffs
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And the plate that the attenuators mount to isn't touching the BeePre chassis at all?
The idea here is that if there's a short from pin 7 of the switch to the chassis, then lifting the attenuator mounting plate off the BeePre plate will disrupt that connection and you should be able to then measure your 5K reading properly. It's not enough to just remove the screws if the two pieces of metal are still touching.
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Ok I'll try again. but I think the best way to do that is to really remove the stand offs
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I removed the stand off and placed paper under it. I still reads 0 kohm
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I would double check that the white and black wires leaving the coarse attenuator are going to the correct spots. They kind of have to be because the stock build wouldn't worth otherwise, but it's worth examining.
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Those just come from the left output jacks. Can the attenuator have a factory defect? I know I did the soldering correctly. Would want to resolve this issue before the end holidays. Also I ordered a Crack, if there is a need to return and have something replaced I suggest to have it shipped together with it.
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Could you double check that the fine switch doesn't have any influence on this reading? In your photo that you posted, it could actually be the fine switch that is making contact where it shouldn't be, so that's worth double checking.
There's a very good chance that if we sent you a new coarse switch and new resistors that you would be back here with the same problem, so let's take the time to properly sort out what's going on before throwing parts at the issue.
-PB
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So I desolder the red and white wires connecting the coarse and fine? and recheck the resistance again?
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No, switch the fine control to a different setting and be sure that doesn't influence the reading you're getting.
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Hi PB, tried switching the fine attenuator, sometimes it stayed at 5 kohm sometimes it goes to 0 kohm at Terminal 7 of the coarse attenuator. It is not on a fix switch setting. Initially I thought it was the fine attenuator Terminal 2 and 8 but turning it to different positions the results become variable but always 5 or 0 kohm. The resistance at terminal 1 was stable at 5 kohm despite switching different positions.
Finally a ray of hope. Think that narrows down the problem, but I'm not sure what is still causing the problem. Hoping to fix this soon, before Christmas.
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PB:
I pulling up the metal plate where the attenuators are secured. Noticed it had a lesser chance of getting a 0 kohm reading. Must be the metal plate shorting it with something. How do I get rid of that? Do I put back the standoffs and see what happens or do I add some insulators in between?
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You would have to use nylon spacers instead of metal, but you should actually find the short and correct it.
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There would need to be debris or a contact between the metal hardware of the switch and the actual switch terminals themselves. This should be easily visible if you inspect the switches closely.
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Finally resolved the problem did 3 things:
1. I changed the number 6 washers to paper washers that I stashed away in my tool kit. I harvested those from my old personal computer motherboard those were used to prevent shorts from the chassis to the computer MOBO.
2. I tightened the hexagonal washers that locks the attenuators to the metal plate. noticed when the shaft touches the metal plate it also caused a short.
3. Sprayed and brushed the contact points. And Voila, shorts gone.
Thank guys. Guess I'll be hearing Christmas carols on my pre-amp after all.
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I've got a new problem, after completing the upgrade and inserted the tubes and turned on the pre amp the left tube is not lighting up and it does not even warm up. How do I trouble shoot it?
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also no sound from the left channel but the right channel seams to be ok
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I would recheck your voltages. The twisted green pair of wires leaving the first PC board you installed in the original build is what makes the tube glow, but you could have a loose solder joint going to pins 1 or 4 on that socket as well.
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Hi PB:
I tested the filament voltage supply at the Reg+ Reg - that is connected to the B1 and B4. show a voltage around the 2.5. The other side Reg+ and Reg - supplying the A1 and A4 was correct 6.3 volts.
Do I desolder and resolder again the incorrect Reg+ Reg-? shaking it still reveals a firm connection. Hope it just a simple problem
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On the front of that board there are pads that say "+ DC -", what voltages do you see at each set?
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The ones on the front both are 8 DC volts.
Just a correction on the Reg+ Reg- connected to the B1 and B4 show a DC voltage of 1 volt. While the Reg+ Reg- connected to the A1 and A4 show also 8 volts
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Neither regulator appears to be working, or there's an issue with your meter that's not letting you resolve the measurement properly.
The 1V could be because there's a short at the socket wiring that's pulling the regulator down, or there could be a soldering issue on the board itself. I would pull out either the wire leaving Reg+ or the wire leaving Reg - (you don't need to do both, just the one that's easy), and see if the voltage coming out of the board pops back up to 6V.
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Verified that my tester is correct, used my friends multi-tester. So What we did unscrewed the filament board and re-checked and added solder to some joints we think has loose joints. After which we checked again the voltage is now correct, and both tubes now light up.
I thought that was it, when we turned on the music. I still have no sound on the left channel. But the right channel sounds great!
I'll check again later tonight. I'll begin with the speaker cables just in case something also got loose.
I also tried switching the cables to channel two and three still no sound on the left channel.
Where do you suggest I check inside the pre amp?
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I found the voltage problem causing no sound on the left channel:
Having the Black terminal at 14
These are the readings on the red terminal:
Terminal 25= 13 VDC
Terminal 30= 13 VDC
Terminal 6 = 120 VDC
Terminal 16= 65 VDC
I've already installed the first upgrade. Are the values for the original build still holds true? The Beepre Manual says Terminal 25 and 30 should be 10. Is 13 volts still okay?
What could be the problem at Terminal 16, is it just loose or just improper soldering at Terminal 16?
Hoping this is the last problem
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I also checked these terminals with the C4S
Black Terminal at 4U
Terminal 1= 170 VDC
Terminal 11= 170 VDC
Terminal 6= 120 VDC
Terminal 16= 65 VDC
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The first BeePre upgrade will slightly raise that voltage.
I would suggest rechecking that the problematic DC resistances you found originally aren't still there.
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All of my resistance problems are fully resolved. I've went through the list.
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The 65V at terminal 16 is troubling. Could you post some build photos?
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These are the photos near the build
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What I would do next is to remove the connections to the large C4S board, rotate it 180 degrees, then reinstall it. If the 65V voltage moves to the other side of the amp, then you have an issue with your C4S board.
Also you should not have to use the isolating parts for the BeeQuiet, and I still believe you have contact between the switch terminals and the metal body of the switch somewhere that's causing issues with that portion of your build.
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I flipped the C4S and re installed it (mirror image from previous). The 65V still on the same side terminal 16. So the C4S is good. Still not sure what's causing the low voltage in 16.
How about the voltages on Terminal 1 and 11 which reads 170v is that okay? Manual says 150V
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The 170V isn't particularly concerning.
Can you post the voltages on pins 1 and 4 of each 4 pin socket?
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with the 300b on? where do I connect the black lead of the tester? What ranges do I expect? So I can set the DC voltage range.
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DC voltage, 300Bs installed, black probe can be on terminal 4.
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A1= 18 V
A4= 13 V
B1=13 V
B4= 18 V
Did I reversed a connection somewhere? heheh...
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No, there's nothing wrong with those voltages.
I suspect that the grid on the offending side isn't seeing a good ground reference. Did you see 65V when testing the installation of the C4S board? I would suspect that you have a loose resistor on the terminal strip next to the input selector switch, or possibly a loose wire on that terminal strip.
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During the first installation of the C4S everything was fine. I think it is solder loosening, cause even the filament board that was the problem. My friend help me look for the joints that did not have enough lead. Think problems came out when kept on tapping and shaking the chassis after trimming joints. So you suggest re inspect terminals 16-20 and 26-30, N1-N5. Add more soldering lead to it.
But the voltage problem is at Terminal 16 and probably B2 since a red wire is connected between the two
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I finally found the problem, yes it was the terminals near the the line selectors, the white wire connected to N1L got disconnected. I think it got snagged by the metal plate holding the attenuators. That wire most likely caused the shorts that I experienced when I was building the resistors at the coarse attenuators. I followed your recommendation and removed the paper washers and returned the #6 washers included in the kit. Did voltage and resistance checks all are in perfect ranges. Connected my DAC to Line 2 then to my headphone amp, sounds great no his or hum, both headphone cups have equal volume, no channel imbalance. Thanks for being patient with me, pointing out my mistakes, also a big thanks to my electrical engineer friend who was willing to help me and trouble shoot the pre-amp during Christmas day.
Still have no sound on my left speaker though, when the DAC was connected to Line 1. I think it is is just the speaker wire connection or again a loose Line 1 solder, but it most likely the former. I can handle it from here. I'll check Line 1 and 3 tomorrow.
Guess this problem is resolved.
I'll work on upgrade 2 mid 2023, meantime relishing upgrade 1.
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I'm glad you stuck with it and got it sorted out!
-PB