Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: Adelz on May 22, 2015, 02:16:14 PM
-
After installing my Speedball upgrade, some of the voltages are way above where they're supposed to be. I've checked for a loose connection but haven't been able to find one. The glow in my tubes appears to be even on both sides and all the LEDs light up; the ones on the main PC board and 9 pin socket are very bright and the ones on the small PC boards light up but are dim in comparison. My voltage measurements are below - highlighted in yellow are the numbers furthest from their intended amounts. When testing audio, the sound from the source is not distorted or muffled. There is buzzing in the left channel; when the volume is completely off, the buzzing goes away, but once it's turned up it becomes immediately audible. What's the best course of action from here?
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fpuu.sh%2FhX0zT.png&hash=3c278612d6918d5046a8024a2abd5edc09eb1452)
-
Please double check the R1 values on each board.
-PB
-
On the small boards, the voltage of the 31.6K resistors on the R1 positions measures 185. On the large board, both have a voltage of 0.
-
Measure the resistance of each actual resistor. I think you have a pair of them swapped.
-
Thanks very much for the help! I did have two of the resistors swapped. All the numbers are perfect now.
When I power it on, though, there's still a very loud buzzing in the background. As all the voltage measurements are within range now I'm really not sure what's going on.
Edit: I'm still experiencing this fairly loud buzzing in both channels; when the volume is turned all the way down, it's very soft, and when turned up the buzzing gets louder. All the LEDs glow and are in the correct position. The 2N222A transistors are both on the small boards and the 2N2907As are on the large board. The 237 ohm resistors are on the small boards and the 31.6 ohm resistors are on the large board. There are no solder bridges between the TIP-50 or MJE-350 transistors.
I've swapped out the tubes and the problem remains the same. All of the voltages are normal (A1 and A6 on the 9 pin socket read 76 instead of 90, but I assume that's close enough). Before installing the Speedball upgrade, the amp functioned perfectly. What should be my next step for troubleshooting this problem?
-
I would be looking for loose filter capacitors that may have been knocked loose during the modifications.
-PB
-
I checked and resoldered all three filter capacitors and the problem is unchanged. Oddly enough I think one may have been a little loose, but the buzzing is still as loud as ever.
-
A loose black ground wire can also cause this issue, though it seems less likely.
-
Which wires specifically should I be sure to check?
-
Which wires specifically should I be sure to check?
All of them (there aren't that many)
-
All of the ground wires are secure and all the grounds listed in the stickied thread measure zero.
I think I've found the problem. It seems the rocker switch is malfunctioning. I turned it on regularly but when I went to turn it off, even in the off position the amp was still powered on. I'm assuming I need a replacement.
-
After rereading your post, do you get buzzing with a source connected?
-
Yeah, I do.
-
I'd go ahead and just reheat all your solder joints. This is the most often cause of the symptoms you describe.
-PB
-
Okay. Do you think it could be the switch, though?
Also, I have a ground wire between Terminal 4 and 14U instead of 22L. That's still fine, correct?
-
Okay. Do you think it could be the switch, though?
The power switch? No.
Also, I have a ground wire between Terminal 4 and 14U instead of 22L. That's still fine, correct?
No problem there.
-
Oh, it isn't? The revision in the Crack manual says it's fine and nowhere does it mention that the revision will not work with the Speedball.
Anyway, I switched that ground wire from 14U to 22L. That didn't fix the problem. I really don't know what to do next.
-
Sorry, I mistyped there.
I have repaired several Cracks recently that had the symptom you are describing. All of them had cold or loose solder joints that needed to be reheated to function quietly.
-PB
-
Ah, okay. Do you think any resoldering of the PCBs will be necessary or does the buzzing mean that it is most likely a transformer/capacitor issue?
-
Ah, okay. Do you think any resoldering of the PCBs will be necessary or does the buzzing mean that it is most likely a transformer/capacitor issue?
Solder joints on PC boards are generally much easier to inspect (there is a lot of online information about soldering PCB's), but it won't hurt to reheat them also.
-PB
-
I've resoldered pretty much everything and the buzzing is unchanged.
I really can't tell what the problem is. Also, thought I'd mention I have the resistor mod for the pot installed but other than that everything is completely stock.
-
I removed the Speedball upgrade and it seems that the amp is working, so it appears that the problem is not the power supply. What are the most common mistakes to look for on the PCBs? Also, is it possible to install each of the PCBs one by one in order to see where the problem is?
-
You can put just the small boards in, then run the amp with the 3K resistors in place (and the 22.1K resistors removed).
-PB
-
The buzzing is back with only the small PCBs in place; I guess that narrows down the problem.
-
Is this noise that you get in both channels?
-
Yeah, I'm getting the noise in both channels. Even after resoldering I'm still getting it; not sure what's wrong.
-
Can you try connecting a source and listening to the amp? With unshorted inputs, you may end up getting some noise.
-PB
-
When plugged into my source I can hear music over the buzzing. The music is not distorted at all and the buzzing now appears to be softer in the left channel in comparison to the right. Right now I have the 3K resistors in place of the large PCB and the two small PCBs in the amp.
-
After a day of troubleshooting the problem is still exactly the same.
It's definitely not the power supply or anything that's in the stock Crack, as that works fine. It seems that the buzzing is being caused by the small PCBs but after resoldering every joint on them the problem remains. What should I do next?
Edit: With the large PCB and the 22.1K resistors between the red wires meant for the small PCBs, the amp functions perfectly, so I'm assuming that the connections of the red wires to the terminal strip are fine. All four resistors on the small PCBs measure correctly, even when measured from their solder joints on the boards. All four LEDs glow brightly and are in the correct orientation. At this point I'm assuming the problem is either one of the MJE350 transistors or a 2N2907. What is the most accurate way to test them?
-
If you believe the transistors are the problem, then they should be replaced. It's possible that one set of transistors was damaged from the R1 swap, but not both sets.
-PB
-
The transistors on the small board with the swapped resistor would be the ones most likely to be damaged, correct?
-
Yes.
-PB
-
Is it okay to test the circuit with one of the small PCBs and one 22.1k resistor? That would definitely help with confirming the problem.
-
Yes.
-PB
-
Both boards are causing the same buzzing sound. Do you think that there are blown transistors on each board or could something else be the cause of the problem?
-
could something else be the cause of the problem?
Yes, I think you have an issue elsewhere. I still believe that you have an iffy connection in your amplifier, and the Speedball constant current sources are simply more sensitive to the issue than the stock circuit.
There could also be an environmental problem close to the Crack (computer, wifi router, etc.) that could be causing some interference. It might not hurt to try the amp in another room.
-PB
-
I tried a different location and interference doesn't seem to be the problem. I guess I'll go through and resolder everything again.
-
I've once again resoldered pretty much everything. Where should I go from here? I really don't want to just continuously resolder every joint; I feel like after all of this it is almost definitely a problem with one of the components. Could the transformer itself be causing the buzzing?
-
Could the transformer itself be causing the buzzing?
Easy to check, make the screws are all tight then add some weight on top of it. Or just push down on it with your hand, but use a piece of wood or something in between....it can be hot!
-
Doing that test didn't affect the buzzing so it appears that the transformer is fine. I'm really stumped about what's causing this buzzing.
-
How long ago did you buy your speedball kit?
-
I bought the kit on April 16th (+/- a day) during the sale. I built the stock Crack for someone I know and am now installing the Speedball on my (roughly 6 month old) amp.
-
OK, I was just checking to make sure this wasn't an older kit from a year or two ago. We had a few that had counterfeit transistors back then. But not in the current kits, those transistors are legit.
-
Ah, okay. Do you have any input on what may be causing the buzzing? I've resoldered all the connections around the transformer and filter capacitors multiple times. All my voltage readings are correct. The amp functions perfectly with the large PCB installed and the 22.1K resistors instead of the small PCBs. I really don't know what to do at this point.
-
Peebs is the designer and the expert on this. I am inclined to agree with his assessment that, if it isn't a miswire or bad solder joint, there may be a problem with the transistors on the small boards. Replacing them might help.
That said, it seems more likely that it would be a cold solder joint or a miswire. It's not uncommon to miswire something on one side of the amp and then unknowingly replicate the mistake on the other side during the build.
-
Okay, thanks.
I've continued to check every connection and joint and I can't find anything wrong. I've resoldered everything and the problem remains the same. Also, now it appears that two of the LEDs on the large PCB are not lighting up during operation either. There must be a defective or dead transistor or something . . . or else I'm completely out of ideas.
-
It sounds like other connections have been disturbed... Could you post as many photos as possible of your build?
-
Sure. I'll post some soon.
-
http://imgur.com/a/St4vU (http://imgur.com/a/St4vU)
Above is an image album of some photos of my amp. I currently don't have the small PCBs in the amp so if you want pics of those installed I can put them back in. I still have the large PCB in the amp, however the two LEDs closest to the 9 pin socket are no longer lighting up at all. If you want any additional pictures I'll take them right away.
Edit: I don't know what went wrong with the two LEDs but I replaced them and those are lighting up now. Still the same buzzing with the small PCBs, though.
-
I'm still stuck with the buzzing. I've replaced and resoldered the red and black wires that attach to the small PCBs just in case but those didn't seem to be the problem either. Have you looked at the photos yet (if you want to see anything else I'll take some)?
-
One thing you might try is moving the wiring from the input jacks to the pots as close to the edge of the panel as possible.
Those little Speedball boards do make the amp a little more sensitive to certain things, though we rarely see an issue like this when the voltages are spot on.
-PB
-
Moving the wiring between the input jacks and the pot didn't change the buzzing at all. After all the resoldering and rewiring I've done I'm fairly certain that the problem must be on the small PCBs themselves. The amp is completely stock minus the resistor mod and the startup voltage modification for the 1/4" jack in the stickied thread, but I'm guessing those small changes wouldn't be the cause of the problem.
-
I think I'm going to get some replacement transistors for the small boards. At the moment one of the boards works but still causes buzzing and the other board's LEDs will not light up (tried fresh LEDs as well, so it's not them, and tried the board in both channels), nor will the corresponding LED in the 9 pin socket. I've resoldered all the wires and capacitors around the transformer and replaced and resoldered the wires that attach to the small PCBs. I figure that having the resistors switched at the start must have damaged the transistors on the small boards.
Also, the large board is currently installed, and with the 22.1k resistors, it works fine. The problems caused by the small boards occur whether the large PCB or the 3K resistors are installed, so I believe that the large PCB is functioning correctly.
-
What voltages do you have with the iffy small board?
-
I installed the iffy board on the standoff nearest the headphone jack. Regardless of the side it's on the two LEDs do not light up (plus one of the two in the 9 pin socket). All voltages are normal except for zero at Terminal 1 and 50 at Terminal 7.
-
Do you have any recommendations as far as what I should do next? I'm fairly certain it isn't a bad solder joint due to all the resoldering and reflowing of solder that I've done. Would more photos be useful?
-
Zero volts at terminal 1 indicates a fault in the small C4S board feeding that terminal.
-PB
-
Yep, that would be the 'iffy' small board where the LEDs aren't lighting up, I'm assuming a transistor is defective. Can I get a free replacement through Bottlehead's replacement parts email?
-
Yes, but please replace both the 2N2907 and MJE350.
-
I did some testing this morning, and it looks like some counterfeit transistors made their way into our inventory. We will be shipping out replacements when we receive a replacement batch shortly.
Replacing the 2907 will cure this issue.
-PB
-
Thanks so much. Oddly it's kind of a relief to me that the transistors are most likely the problem, I'm glad that the problem isn't something else in my amp because as I've said, I'm at a loss after all this resoldering. Thanks for all your help thus far!
-
Just wanted to double check - is it fine to use the Crack with only the large PCB and the 22.1k resistors in place of the small PCBs for extended periods? Just want to be sure that having half of the Speedball upgrade installed until the authentic transistors ship out will be okay.
-
Yeah, no problems there!
-
I did some testing this morning, and it looks like some counterfeit transistors made their way into our inventory. We will be shipping out replacements when we receive a replacement batch shortly.
Just wanted to add a second case. I have exactly the symptoms described by the OP and have gone through the same exercise and have isolated the issue to the two small PCBs. Currently back to the 22.1k loads and the large PCB. Not sure if it's placebo, but with just the large PCB I can already hear a significant improvement in the sound (on HD 650). There is far less veiling and the sound is brighter. The mids are singing, although were great, now the highs are almost as clear as the mids. Bass is deeper. There is only an ever so slightest background noise at max volume.
Details:
Ordered on the 14th of April, shipped May 14th. The vanilla Crack worked on first power without a hitch (thanks for a fantastic product and an amazing guide). The sound was actually better than I was expecting (first Tube amp, was expecting higher harmonic distortion, background noise, and rolled-off highs... none was true).
After upgrading to the Speedball, I had an annoying buzzing without having a source (on connecting a source does play the music, but the buzzing is very audible throughout). All voltages were within range (<10% of the ratings). LEDs all light up as expected (after a few seconds, the 2 on the 9pin socket and those on the small PCB light up rather quickly, then slowly the ones on the large PCB come to life and are brighter than all the others). The buzzing sounds like 120hz and it's loud even on lowest volume. It actually goes quieter when I turn the volume knob (but never acceptably quiet,) until I hit past two thirds, then it's loud again. I resoldered all joints, no help. Quadruple checked the circuits, all look good. The warm-up DC on the jack climbs past 20 and hits high 30s. Without Speedball it never crossed 15V.
The buzzing is worse where there is WiFi. Away from WiFi source and simply moving my hand around the small PCBs make the buzzing volume changes significantly. Furthermore, touching the chassis or the pot changes the buzzing as well (touching the RCA changes nothing). Clearly the small PCBs are picking (and amplifying) RF, or at least the buzzing is modulated by RF. I can't verify the authenticity of the 2907, but I'll mention that their package sizes are different (one is shorter than the other).
After removing the small PCBs and resoldering the 22.1k loads, the background is very quiet, no buzzing or other noise.
Please let me know what I need to do to get replacement parts or other remedy to fix the issue. Although I'm very satisfied with what I have now, I'd like to get the full shebang.
Thanks again for a remarkable product!
-
Glad to hear that it seems to be the transistors causing the problem. Bottlehead's replacement parts service sent out an email announcement and said that the replacement transistors will be shipping out sometime next week.
-
Hadn't noticed the mail. Thanks for the hint.
-
I installed the iffy board on the standoff nearest the headphone jack. Regardless of the side it's on the two LEDs do not light up (plus one of the two in the 9 pin socket). All voltages are normal except for zero at Terminal 1 and 50 at Terminal 7.
I just received my replacement transistors and installed them on the small boards. The LEDs on the board mentioned in the quote above still do not light up. I switched the 2907 transistors between the two small boards and both the transistors work correctly on the functional board, so there must be a different problem with the faulty board. I also switched the positions of the boards in the amp and that made no difference; on either side one of the boards did not light up and the other did. Many of the voltage readings are also off. Terminal 1 = 0, Terminal 5 = 142, Terminal 7 = 49, Terminal 9 = 142 (measurements taken with the faulty board near the headphone jack and the functional board near the pot; readings not listed are normal). Where should I go from here?
-
I also switched the positions of the boards in the amp and that made no difference; on either side one of the boards did not light up and the other did.
Did the bad board/voltage switch sides (board problem), or not (wiring problem)?
-
Yeah, the problematic voltages shifted sides with the faulty board and the functional board works on both sides, so I don't think it's a wiring problem.
-
Now, what happens if You turn the big board around 180 degrees and leave the small boards put?
-
Yeah, the problematic voltages shifted sides with the faulty board and the functional board works on both sides, so I don't think it's a wiring problem.
That would mean it's a board problem.
If you e-mail [email protected], we can put together a parts kit to replace that board. Please provide your name, kit, parts desired, and shipping address.
-PB
-
Okay, thanks. I want to test everything one last time. Unfortunately I'm pretty busy right now so I'll email for replacement parts in a few days.