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Post by Deleted on Jun 14, 2015 21:15:39 GMT
Is it an electrolytic capacitor, or a small ceramic capacitor ? If the latter, it is still likely to be an earthing problem in the front end most likely, assuming that the output from the capacitor multipliers is a clean supply.
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Post by Deleted on Jun 14, 2015 21:18:54 GMT
Is it an electrolytic capacitor, or a small ceramic capacitor(22pF not 22uF) ? If the latter, it is still likely to be an earthing problem in the front end most likely, assuming that the output from the capacitor multipliers is a clean supply.
Alex |
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Post by blackeyeliner on Jun 14, 2015 21:54:52 GMT
Is it an electrolytic capacitor, or a small ceramic capacitor(22pF not 22uF) ? If the latter, it is still likely to be an earthing problem in the front end most likely, assuming that the output from the capacitor multipliers is a clean supply.
Alex Small cerapic capacitor, 22pF of course, you're right. So, still an earthing problem, but absolutely unknown where. How do I check the supply at the output of capacitor multipliers? |
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Post by Deleted on Jun 14, 2015 22:17:29 GMT
Small cerapic capacitor, 22pF of course, you're right. So, still an earthing problem, but absolutely unknown where. How do I check the supply at the output of capacitor multipliers? Look at their output using the AC input of the Oscilloscope. If both channel outputs look the same, then try soldering BOTH sides of the PCB where the 2 lots of 3 potentiometer connections are. Any vacant holes, (vias) insert in a piece of tinned copper wire and then solder both sides. |
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Post by PinkFloyd on Jun 15, 2015 19:03:49 GMT
I can't remember if the problem was hum related but I discovered (after MUCH probing) that the ground pad was not attached to the ground plane and this was the fix:  |
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Post by blackeyeliner on Jun 15, 2015 20:40:49 GMT
So I soldered all ground pads of volume potentiometer together - no effect. I think I really have a reliable ground on the volume potentiometer. I checked the capacitor multiplier outputs - as far as I was able to understand, these are the outputs near R3, R5, R15, R16 resistors? It's clean and both channels look the same (basically, it's static with no significant ripple or anything). What is interesting is that I connected every ground together again and this time the static noise floor became lower, while the hum was more prominent on the screen. It's clearly a square wave, or something that looks like a part of the sinus, passed on by a diode (maybe?). Also, it's in sync with power supply ripple. Blue line the ripple found on one of the large 3600 uF capacitors in the power supply. Yellow line is the headphone output.  |
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Post by PinkFloyd on Jun 15, 2015 21:05:21 GMT
So I soldered all ground pads of volume potentiometer together - no effect. I think I really have a reliable ground on the volume potentiometer. I checked the capacitor multiplier outputs - as far as I was able to understand, these are the outputs near R3, R5, R15, R16 resistors? It's clean and both channels look the same (basically, it's static with no significant ripple or anything). What is interesting is that I connected every ground together again and this time the static noise floor became lower, while the hum was more prominent on the screen. It's clearly a square wave, or something that looks like a part of the sinus, passed on by a diode (maybe?). Also, it's in sync with power supply ripple. Blue line the ripple found on one of the large 3600 uF capacitors in the power supply. Yellow line is the headphone output. You lost me on the second paragraph mate, I'm sorry, erm....... I'll get my hat and coat. Mike. |
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Post by blackeyeliner on Jun 15, 2015 21:08:49 GMT
You lost me on the second paragraph mate, I'm sorry, erm....... I'll get my hat and coat. I am sorry  Simply put I wanted to say my hum is a square wave, and it's synchronized with ripples in the output of the power supply. Also I did what everyone suggested before, no effect. |
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Post by Deleted on Jun 15, 2015 21:38:19 GMT
You lost me on the second paragraph mate, I'm sorry, erm....... I'll get my hat and coat. I am sorry Simply put I wanted to say my hum is a square wave, and it's synchronized with ripples in the output of the power supply. Also I did what everyone suggested before, no effect. Again, if the output from the capacitance multipliers is clean, then the problem is still most likely due to earthing in the input area of the amplifier. This may be due to poor PCB design in this clone of the original , OR your set up. I haven't seen photos of the amplifier as connected, but even then, remote diagnosis of a problem like this is not always possible. You should be sorting out the problem with the vendor, who may have seen this problem before.
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Post by blackeyeliner on Jun 15, 2015 21:45:52 GMT
I am sorry Simply put I wanted to say my hum is a square wave, and it's synchronized with ripples in the output of the power supply. Also I did what everyone suggested before, no effect. Again, if the output from the capacitance multipliers is clean, then the problem is still most likely due to earthing in the input area of the amplifier. This may be due to poor PCB design in this clone of the original , OR your set up. I haven't seen photos of the amplifier as connected, but even then, remote diagnosis of a problem like this is not always possible. You should be sorting out the problem with the vendor, who may have seen this problem before.
Alex Could you help me identify the points on the schematic where I can correctly measure the output of the capacitance multipliers? I might not be doing this correctly. |
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Post by Deleted on Jun 15, 2015 22:30:58 GMT
The emitters of Q3 and Q12. The arrow shown on the transistor drawing is the emitter connection. Any of the resistors shown as connected to those points will do.
Alex P.S.
I don't like the look of the volume control pads underneath the PCB. There is no solder flow evident through all holes. If the volume control has been installed, it's pins are not extending right through the PCB to ensure a good connection between both sides of the PCB. You can't rely solely on the through plating between sides. which can be easily damaged by insertion of tight fitting component leads. They should be soldered on both sides.
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Post by blackeyeliner on Jun 17, 2015 19:35:22 GMT
The emitters of Q3 and Q12. The arrow shown on the transistor drawing is the emitter connection. Any of the resistors shown as connected to those points will do.
Alex P.S.
I don't like the look of the volume control pads underneath the PCB. There is no solder flow evident through all holes. If the volume control has been installed, it's pins are not extending right through the PCB to ensure a good connection between both sides of the PCB. You can't rely solely on the through plating between sides. which can be easily damaged by insertion of tight fitting component leads. They should be soldered on both sides. Seems like the outputs of capacitance multipliers are different. This is the 669 emitters - top is the faulty right channel:  and this is the 649 emitters:  Definitely there is something wrong going on in the right one (yellow graph). I agree on the potentiometer holes - they are damaged. I triple checked grounding, and it's there, so if the capacitance multiplier output is not the cause - I will just order a new kit. |
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Post by blackeyeliner on Jun 19, 2015 8:43:16 GMT
So I guess it's really a grounding issue due to damaged board. Ordered a new one - this one goes to disassembly... Thanks everyone for your involvement and support!
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Post by blackeyeliner on Aug 8, 2015 21:50:38 GMT
In case anyone was wondering, I finally found the reason of hum that appears to be in ALL pandas more or less (in some - 2mV, in some around 1 mV).
So I built 3 of them and they all are faulty like that. The hum is induced by the headphone protection circuit, which is powered by a 1N4148 diode. This diode produces impulses that are somehow (not sure how, really) induced on the right channel.
Shorting out the relay and cutting down power of the protection scheme solves the problem 100% and hum is gone both sonically and on the oscilloscope. However, it's still unclear how it gets there and if there is any way to keep protection circuit working while stopping the hum.
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4c
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Post by 4c on Jan 26, 2016 22:20:08 GMT
OK, So I'm a mite late to the party, and it's three years since I bought the kit from Mike, but I'm finally underway! In my defence, I have been creating small children recently. I've now produced a grand soldering platform to protect the house from flying solder and tumbling irons. And I've begun to populate the board with the low profile stuff (not soldered yet). First question, what's a reasonable solder to use? I currently have: - Antex Sn99.25 Cu0.75 0.8mm Lead free Solder,
- BernzOmatic "Silver Bearing Lead Free Solder" 2.4mm
- Archer 60%tin 40% lead .062" (from Tandy!)
I'm not sure I have enough of the Antex or Archer to complete the job, and the Bernzomatic at .093 is pretty thick stuff. I've looked up some of the recommendations from the early pages of the Panda VFM thread, and it's approximately £39! I'll post a couple of pictures once I've learnt how, I'm too busy wading through the 48 pages of the VFM thread at the mo, harvesting the good stuff. Tom. |
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Post by jc on Jan 26, 2016 22:44:33 GMT
Crikey! You may have beaten my record for a slow build  You'll want to be using the leaded solder "Archer 60%tin 40% lead .062" (from Tandy!)". The lead free stuff is a pig to work with, especially if you're using a standard soldering iron. |
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Post by parrymike on Oct 7, 2019 13:50:44 GMT
So I built my Panda back in 2012 and was wondering on how much the world has moved on since then. Do you still think the Panda is a great amp. Have things moved on much over the last few years? Is anybody still here?
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Post by 4c on Oct 7, 2019 22:11:17 GMT
Hi all,
parrymike 's timing is perfect. Tonight the (probably) very last Panda was born: It was a difficult delivery that started yesterday, but led to smoke whenever it saw the full 18V. In the end I spotted today that I'd somehow installed a TIP42 in a TIP41 slot, despite checking a thousand times. I managed to remove the TIP42, only partially lift some pads, and then install the TIP41. After some tentative continuity checks, Panda was fired up and works. Now it measures 1.5V across the 1k5v resistors, and several piddlyvolts DC offset on both channels. As this has been a 7 year journey (admittedly not 7 constant years of effort), I'm overly excited about getting to this stage. Next up, case installation. So I'm hoping that, in response to parrymike 's question, everyone is about to reply and claim that the Panda is still the best amp out there for under £400. Although secretly, I'm starting to hope that there's another new DIY bargain that will keep me busy until 2026. I've never heard a valve amp, so maybe that's where I should go. Or perhaps I should finish the Panda first... And did anybody ever collate a list of the best upgrades to do once you've finally got the Panda working? I know Mike built several, but did they ever get compared?!
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Post by parrymike on Oct 9, 2019 14:17:23 GMT
Congratulations on finally finishing the build. That HAS to be a record! I was so proud when I'd finished mine that I felt a bit sad hiding it away in a case. That blue board is beautiful.
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Post by PinkFloyd on Oct 9, 2019 20:22:21 GMT
Hi all,
parrymike 's timing is perfect. Tonight the (probably) very last Panda was born: It was a difficult delivery that started yesterday, but led to smoke whenever it saw the full 18V. In the end I spotted today that I'd somehow installed a TIP42 in a TIP41 slot, despite checking a thousand times. I managed to remove the TIP42, only partially lift some pads, and then install the TIP41. After some tentative continuity checks, Panda was fired up and works. Now it measures 1.5V across the 1k5v resistors, and several piddlyvolts DC offset on both channels. As this has been a 7 year journey (admittedly not 7 constant years of effort), I'm overly excited about getting to this stage. Next up, case installation. So I'm hoping that, in response to parrymike 's question, everyone is about to reply and claim that the Panda is still the best amp out there for under £400. Although secretly, I'm starting to hope that there's another new DIY bargain that will keep me busy until 2026. I've never heard a valve amp, so maybe that's where I should go. Or perhaps I should finish the Panda first... And did anybody ever collate a list of the best upgrades to do once you've finally got the Panda working? I know Mike built several, but did they ever get compared?!
Congratulations on the birth of your Panda! Nice to see that  I built "quite a few" Pandas but, these days, am not at all tuned in..... spending my time (these days) feeding daft pheasants peanuts Nice job man...... do your ears appreciate the fruits of your labour? Mike. |
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4c
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Post by 4c on Oct 14, 2019 21:39:24 GMT
No cigar. Amp now housed in the case and given time to 'burn in', DC offsets set to damn near 0mV for both channels. But, one channel has no bass and the mids/treble are echoey. I expect this is caused by damage when I turned it on with a TIP42 (pnp) installed instead of a TIP41 (npn). There was a brief wisp of smoke when I turned it on (then quickly off), but I spotted the problem and installed the TIP41. So, it's off to my Dad's to hook it up to a signal generator and start trying to track down the damaged component(s). My question is: which components are likely to be the ones that are damaged? I've provided a close up of the zone of smoke. It was the TIP42(1) attached to the heatsink that was wrong. If there are some obvious contenders, I might buy the components in advance rather than spend separate sessions fault finding and then replacing. I don't want to wait another six years!! |
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Post by PinkFloyd on Oct 15, 2019 19:10:08 GMT
Hi Tom, That echoey bass shy sound you describe sounds more like something at the output end of the amp. I would be looking at the physical connection between the output and the headphone socket...... those screw down terminals are notoriously shitty and the fact that you have connected the ground wire to the RH channel (on the headphone socket) is probably all that's wrong Maybe it's just the photo quality playing tricks but it looks like you've wired up R to G (on the headphone socket) that's where the problem lies mate. Swap those wires over and it will work fine...... It's always the simple stuff that is overlooked (been there / done that) so a simple wire swap should have you smoking that cigar mate   |
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Post by PinkFloyd on Oct 15, 2019 19:40:32 GMT
When you've got the wires swapped over and smoking your cigar please do upload your panda to the "official show us your Panda" thread It's a shame that most of the global Panda images have disappeared (that's what time, technology and greed does) but happy to see my fleet of Panda amps are still showing..... and so they should be / I pay a small fortune (the price of two average doner kebabs) to keep the photos live but one dodgy doner and I'm dead...... the whole archive vanishes into the ether. The internet is all well and good as long as you are ALIVE and PAYING to keep your shit online for future generations to see...... if you die, it all disappears. Anyhoo, I won't go into rant mode, life is way too short for that. rockgrotto.proboards.com/thread/6604/official-show-panda-thread |
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Post by 4c on Oct 15, 2019 22:37:56 GMT
Mike, You've just taken the last few days of my foul mood, chucked it in the bin, and shone pure sunshine through my ears. It sounds fantastic. I would have replied earlier, but I can't help listening to more tracks. thank you, thank you, thank you, thank you! I know how it happened. Earlier that evening I was soldering up the input leads: Ground in the middle. I wasn't thinking/looking when I hooked up the output leads. I really appreciate the time you've taken to look over it, it was a very generous thing to do. And thank you for starting the whole Panda movement in the first place; I now have a piece of hi-fi that I probably wouldn't have been able to attain at commercial prices. I feel like I've beaten the system and snuck a peak at the high end normally reserved for the rich :-)
I really fancy a doner kebab now. Once I've got the first batch of finger print marks off the case, I will try and find an arty place to photo it and get the pictures up on to the "official show us your Panda" thread. Many thanks again. Right I'm off, time to try some more tracks |
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Post by PinkFloyd on Oct 16, 2019 10:30:45 GMT
Glad to be of help Tom...... nothing worse than the feeling of doom and despair.... enjoy the music mate!
Mike.
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