Hi all! Recently took the plunge down the DIY rabbit hole, putting the fun and passion back in my music listening! I recently purchased a tube amp kit, vendor shall remain anonymous for the moment, and am not able to get output. This particular kit has multiple test points on the PCB and there are a few that do not measure correctly. What is curious to me is with all these test points the kit vendor is unable to assist me other than to say it is either a bad solder joint or misplaced part. Wouldn't the point of having multiple test points to be to help isolate the problem?
^ Without a little more information, it would be impossible to guide you. I don't know what Jon intended, but here's my 
If you're looking for the answer to the indirectly asked question, "Shouldn't they support me throughout my troubleshooting efforts?"; my reply is, no.
The answer to your direct question...
They likely sold you a bag of parts and a board with perhaps a schematic and some instructions. Unless you are claiming that one of the parts (or the board) was defective, then you're on your own.
Your best bet is to use the test points and the schematic to find the fault, which is likely one of three things in a general order.
If you can't get it cracked, post the schematic here along with the values you obtained at each test point.
Sticking this on at the end. Your last post was as I was typing. No. Don't worry about any numerical order.
Mainly... It's awesome that you're diving in. Have a blast, and keep that ACA playing in the background to calm the beast within while you troubleshoot.
Edited to add - I don't know how complete the kit was/is. Another potential failure mode is 'wiring'. If you added the I/O, then you may have mis-wired it.
If you're looking for the answer to the indirectly asked question, "Shouldn't they support me throughout my troubleshooting efforts?"; my reply is, no.
The answer to your direct question...
Yes. You've already said that "They don't measure correctly", so it seems some values were provided.
They likely sold you a bag of parts and a board with perhaps a schematic and some instructions. Unless you are claiming that one of the parts (or the board) was defective, then you're on your own.
Your best bet is to use the test points and the schematic to find the fault, which is likely one of three things in a general order.
- Mis-stuffed part(s) ... if all the parts are gone from the bag, and the intention is to use them all, then it stands to reason that at least two would be in incorrect locations. Also, look on the schematic to see if you need to install any jumpers. A part may not have been provided, but you may be expected to make a wire bridge. Check orientation of diodes / caps etc.
- Bad solder joint
- Bad part. Least likely, but not impossible. They'll likely claim that you damaged it, if it's already installed.
If you can't get it cracked, post the schematic here along with the values you obtained at each test point.
Sticking this on at the end. Your last post was as I was typing. No. Don't worry about any numerical order.
Mainly... It's awesome that you're diving in. Have a blast, and keep that ACA playing in the background to calm the beast within while you troubleshoot.
Edited to add - I don't know how complete the kit was/is. Another potential failure mode is 'wiring'. If you added the I/O, then you may have mis-wired it.
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It's not as easy as you think about it: 'test points' can be anything ( test point asy ou hear them... to point used to set the circuit into a given acceptable margin, etc,etc,...). Without schematic you can only make supposition.
You'll need troubleshoot your circuit. And you are at the right place ( to learn how ) to do it.
First check for parts: orientation ( electrolytics capacitors, diodes,... everything with a +/- mark should be oriented as in the schematic).
Then inspect soldering work. Bad solder joints can be anywhere: re heat the ones looking dubbious.
If from there it still don't work you'll have to trace signal along the schematic: you need a generator ( whatever can send a sinus at 1khz will do: cd player, computer, dedicated function generator).... if you need to generate a sinus at 1khz to burn a cd or have a file to play just ask, many here can do it and send it yo you.
Now you have a known signal availlable, inject it into the circuit ( through input) and follow the path it should follow in the circuit ( in the schematic), testing points along the way to see if it is present or not and non modified ( distorted).
To check you'll need an Oscilloscope, DMM ( digital multimeter) or a small amp+ loudspeaker (with probe for +/- inputs), define the check points you want to test thanks to schematic and locate them on board.
Great learning opportunity.
Edit: ItsAllInMyHead was faster than me!
You'll need troubleshoot your circuit. And you are at the right place ( to learn how ) to do it.
First check for parts: orientation ( electrolytics capacitors, diodes,... everything with a +/- mark should be oriented as in the schematic).
Then inspect soldering work. Bad solder joints can be anywhere: re heat the ones looking dubbious.
If from there it still don't work you'll have to trace signal along the schematic: you need a generator ( whatever can send a sinus at 1khz will do: cd player, computer, dedicated function generator).... if you need to generate a sinus at 1khz to burn a cd or have a file to play just ask, many here can do it and send it yo you.
Now you have a known signal availlable, inject it into the circuit ( through input) and follow the path it should follow in the circuit ( in the schematic), testing points along the way to see if it is present or not and non modified ( distorted).
To check you'll need an Oscilloscope, DMM ( digital multimeter) or a small amp+ loudspeaker (with probe for +/- inputs), define the check points you want to test thanks to schematic and locate them on board.
Great learning opportunity.
Edit: ItsAllInMyHead was faster than me!
@Toys4Boys If it's copyrighted and/or they've specifically told you that you may not share the schematic, then don't post it. Even if it 'feels right', it's against forum rules (and possibly against the law). What you can do... that I think is well within the spirit and intent of copyright law, is to have one or two people virtually look over your shoulder ... you can share copyrighted information within bounds.
Sadly, I can't offer to be one of those people. Mainly... lack of qualification. You don't want me to do it
Sadly, I can't offer to be one of those people. Mainly... lack of qualification. You don't want me to do it
He Is. We have tried phone calls but to no avail. I have gone thru and compared parts values/orientation, and it looks good. Will go thru my solder points again tomorrow.
Ok. So yes, better wait and see how it evolve.
Is there wiring to the circuit board involved ( psu board, satellite with potentiometers, transformers, etc,etc,...)?
If so check this too. In my experience with projects involving circuit boards, 80% of errors comes from wiring mistakes.
Is there wiring to the circuit board involved ( psu board, satellite with potentiometers, transformers, etc,etc,...)?
If so check this too. In my experience with projects involving circuit boards, 80% of errors comes from wiring mistakes.
I have been working with the vendor and have made progress, but...There remains a problem which he believes is impossible. He indicated that I can't post the complete schematic, so I have asked if I could post just a portion, that he pre-approves, could I post. I have a hunch that this may still be a violation of forum rules?
If someone says they will help, you can PM the schematic to them.
Hopefully you have checked all solder joints, and verified all components are in the right locations.
It's common for beginners to switch parts by misreading color codes, so measure resistors instead of reading them.
Hopefully you have checked all solder joints, and verified all components are in the right locations.
It's common for beginners to switch parts by misreading color codes, so measure resistors instead of reading them.
Appreciate your help, I have gone thru twice checking values and orientations, and used my magnifying headband to touch up all solder joints. There are over 10 test points per side and 1 TP is reading 4 times the DC, the vendor says the only thing that could cause this is a bad driver tube. I swapped tubes, no joy.
For someone to help you, they will probably need to see a schematic. It could probably be shared privately, perhaps by email or PM. IOW, it would need to be more or less as though a friend is looking over your shoulder, trying to help you troubleshoot. If you take that to mean your cell phone camera in a live chat session could point at the schematic, that may be within reason. Also, you may have to balance copyright with educational and or other exempted use. In addition it may help greatly if you have an oscilloscope.
Tube amp kit:
1 - is power supply working correctly, supplying the correct voltages where it should?
2 - is it a stereo amp? are both channels not working?
Fault finding is all about narrowing down the area at fault but start with the big picture and the basics.
At least post a link to the amplifier you have to give a clue as to its complexity.
1 - is power supply working correctly, supplying the correct voltages where it should?
2 - is it a stereo amp? are both channels not working?
Fault finding is all about narrowing down the area at fault but start with the big picture and the basics.
At least post a link to the amplifier you have to give a clue as to its complexity.
Thx for helping. It is a stereo amp, the 1 channel measures almost perfectly, 2 TPs are a little low. I tried running my phone in to it w/ no success, but am going to try hooking it up to my system. The other thing I will try is comparing the components around the faulty reading on the side that is working more correctly.
For what it's worth, this is a fairly expensive kit, and while it is most likely something that I did, I would have expected better support. When I first contacted the vendor he had me record the 23 TPs and when I sent him that he said it is either a misplaced component or bad solder joint. I worked it some more and he had me send him new readings of the 23 TPs. Once again told me the prior answer. At this point I was getting a bit frustrated and asked if there are 23 TPs ande 1 is bad can't he point me in a direction. Of course the answer was the same, I really don't need someone having me spend time on 4 occasions measuring TPs to tell me what I already know!
Sorry for the rant, just been festering for a while. Oh yeah, its an Elekit TU8900.
For what it's worth, this is a fairly expensive kit, and while it is most likely something that I did, I would have expected better support. When I first contacted the vendor he had me record the 23 TPs and when I sent him that he said it is either a misplaced component or bad solder joint. I worked it some more and he had me send him new readings of the 23 TPs. Once again told me the prior answer. At this point I was getting a bit frustrated and asked if there are 23 TPs ande 1 is bad can't he point me in a direction. Of course the answer was the same, I really don't need someone having me spend time on 4 occasions measuring TPs to tell me what I already know!
Sorry for the rant, just been festering for a while. Oh yeah, its an Elekit TU8900.
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So just work from the good side of the circuit comparing voltages to the dead channel. At some point you'll find the spot where there's no DC, if that's the issue.
In all fairness, this is a very busy time of the season for some. Christmas is right around the corner, and people have family to deal with.
jeff
First off, thx for taking your time to help. The TP actually measures about 3 times the voltage it should, and the vendor said "The only thing that could cause that is a bad driver tube.". When I swapped the 12BH7A lt/rt the problem remained in the same channel, so much for the driver tube being at fault! Then he fell back to bad soldering.