Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

Ill advised Champ 600 project

Discussion in 'Glowing Bottle Tube Amp Forum' started by Prophetsnake, Jul 15, 2017.

  1. Bendyha

    Bendyha Tele-Afflicted Ad Free Member

    Mar 26, 2014
    Northern Germany
    Nothing at 15, to ground ? What about across J 9 & 10 ? and from each of them to ground? Before you said you had a reading across the filament supply. I hope you have checked Fuse 2

    So what are you readings AC and DC at TP12 & 9 to ground?
     
    Last edited: Jul 17, 2017

  2. Prophetsnake

    Prophetsnake Tele-Meister

    134
    Aug 2, 2016
    ireland
    Doesn't appear to be anything at all from 15 to ground. I did check across J9 and 10 and they have 5.9V
    TP 12 has 390 DC and 859 Ac. TP 9 has 0, but I still haven't put the tubes back, and surely it needs that to complete the circuit? I'm not sure why I was supposed to take them out in the first place, so I'm not sure if it's time to put them back for further testing
     

  3. Bendyha

    Bendyha Tele-Afflicted Ad Free Member

    Mar 26, 2014
    Northern Germany
    First get the supply sorted out, continuity checked, then put the tubes in for the next stage of testing.... a then b then c.... don't jump from the plane till you have checked the parachute is in the backpack and the strings are attached.

    If you have J 9 & 10 showing voltage, but not TP 15 then find out wher the connection is broken...fuse F2....a disconected wire....look, search and find.

    If you have voltage at TP 12 but not J9 then test for continuity between J9 and J4. If there is none....then there is a problem with your output transformer.
     

  4. Prophetsnake

    Prophetsnake Tele-Meister

    134
    Aug 2, 2016
    ireland
    Strange an unexplainable readings all around, and now, my multimeter is acting up, so I will have to abandon the chase until I can get a new one.
    Your comment on the output transformer made me check. No continuity on the power winding! And the tubes are not heating now, they were yesterday. So a lot of strange things going on.
    Thanks so much. I'll post again in a few days, hopefully with a bit of positive news.
     

  5. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    Did you replace the battery in your multimeter? That might be the only problem with it.
     

  6. Prophetsnake

    Prophetsnake Tele-Meister

    134
    Aug 2, 2016
    ireland
    Robrob,

    I did, thanks. It behaves differently when the battery is low. Might be worth a try replacing it again, though.
     

  7. Prophetsnake

    Prophetsnake Tele-Meister

    134
    Aug 2, 2016
    ireland
    Okay.
    Bought a new multi meter and its improved the picture considerably.
    For starters, it's showing 6.4V on the filament winding. And 279V on the other secondary, so that all looks good.
    A lot of the spurious looking AC voltages (300-800) I reported have settled down to zero.
    TP15 still appears to be dead. The fuse is okay, but the tubes are not heating, so I'll have to locate the problem there, obviously.
    There is no continuity on the primary winding of the output transformer, so I'm thinking that that is shot as well.
    With the tubes in, I'm still getting nothing at the TP, which should be indicating tiny voltages, so I figure that that simply means the tubes aren't doing their thing because of the heater circuit.

    One odd thing I have noticed with the new multi meter is that it often gives readings that dissipate to zero or near zero after twent or thirty seconds, or they jump around for no apparent reason. These are usually places where I'd expect to see nothing at all, for example at TP9, where the numbers seemed to jump from say, 181 to 390 and then to zero and finally settled at .4 (AC). Is this sort of thing normal?
    On others it might start off at say 30V and bleed off to nothing. Cap relieving itself?
     

  8. Bendyha

    Bendyha Tele-Afflicted Ad Free Member

    Mar 26, 2014
    Northern Germany
    None of those small AC voltages will be there if the tubes are cold.
    Putting large DC voltages across cold tubes is not a thing one should do!
    Yes, caps can and will cause voltages to change as they blled of through the multimeter.
    Jumping around....does happen....could be various causes...sometimes bad contact of probes, sometimes meter set to wrong range or AC/DC setting, sometimes trying to read across a resistance that is very high......Usually trying to read the right things in the right way in the right places will solve this problem, but when there is a still unknown defect in the circuit, then we don't know if this might be causing the problem.

    Solve those continuity problems with the heater circuit and the out-put transformer, then we might discover more.
     

  9. Prophetsnake

    Prophetsnake Tele-Meister

    134
    Aug 2, 2016
    ireland
    Thank you. I'm slowly beginning to come to grips with this process.
    Having said that, I'm no closer to solving the power supply issue. Nothing appears obviously wrong in the filament supply circuit, though a couple of things seem odd to me.

    All of this is with tubes out, by the way.

    I snipped the diode out and jumped R24, hoping that something magical might happen and all would be good. It would have had to be done anyhow. No luck, obviously.
    The fuse (F2) seems to be ok, but could something else in the circuit make it appear so?
    I've powered the pilot light with a dying 9V battery that is showing around 6V. It glows for a second, then dies out. If I leave it for a minute or two it will do the same again. Could be that the secondary is soaking it up?
    At this stage I am considering bypassing the PC board altogether and wiring the circuit directly.
    Add a fuse holder, the appropriate resistors, either in the control panel or somewhere inside, and connect the power supply somewhere - I'm not sure where, but I'm thinking the socket pins. Any thoughts on this?
     

  10. Prophetsnake

    Prophetsnake Tele-Meister

    134
    Aug 2, 2016
    ireland
    One other thing. The solder joint at WJ2, which is where the light is connected, is a little large and splattery. When I test it connected to either the adjacent end of the fuse or R24, I show no resistance. Now, on the schematic, those points seem to be directly connected. But on the printed backside of the PC they are attached to different strips. I'm not sure what to make of that.
     

  11. Bendyha

    Bendyha Tele-Afflicted Ad Free Member

    Mar 26, 2014
    Northern Germany
    I'm afraid I dont quite get the positions from your description. the two leads from the lamp now join where? can you post a drawing?

    The tracks on those amps PC boards are notoriously delicate. I have had experienc with having to add jumers on one before now. It can happen that a solder spot looks good, but is actually lifted up slightly and split the contact track-disc away from the trace-strip leading away from it.

    If the connections aren't there, then hard wireing the connections is a sturdy alternative. There is no reason why the output transformer lead could not be directly conected to pin 3 of the tube socket.
     

  12. Prophetsnake

    Prophetsnake Tele-Meister

    134
    Aug 2, 2016
    ireland
    I haven't moved the lamp positions, so they're still at WJ1 and WJ2. I am beginning to suspect that this thing didn't pass muster at the factory, and so was pulled and flogged on eBay for a sucker like me to pick up.
    I've got a new OT ordered, and I'll try this rewire trick. I'll get some resistors, and if that plan fails, I will just scrap the lot and build a proper 5F1 to fit the cab.
    Meanwhile, I'll figure out how to upload a pic and post it here...
     
    Bendyha likes this.

  13. Prophetsnake

    Prophetsnake Tele-Meister

    134
    Aug 2, 2016
    ireland
    IMG_6539.JPG

    Based loosely in a 50's Valco. First attempt at one. It has it's faults, but looks good and is sturdy. All pine, finger jointed with a genuine 40s drawer pull on top.
     
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  14. Prophetsnake

    Prophetsnake Tele-Meister

    134
    Aug 2, 2016
    ireland
    Progress! I pulled the two 100 resistors in the filament supply and pulled pretty much everything else out of that entire circuit. The fuse, which had been testing okay in situ, was no good after I pulled it, but maybe I cooked it taking it out. So, perhaps the issue was a short in there all along. Never mind, it's all a wastleland now
    So,I wired the transformer to the 4&9 pins on the pre-amp tube, along with the light and re-claimed resistors.
    Now I just have to wait for my new output transformer to arrive and I can try again.
     

  15. Bendyha

    Bendyha Tele-Afflicted Ad Free Member

    Mar 26, 2014
    Northern Germany
    Good to hear. pins 4&5 are still joined together on the PCB I assume. So you are now without a fuse in the filament supply? This is normally okay, older amps seldom have one there. But I hope you still have the two sides of the filament supply referenced to ground through two 100 Ohm resistors, and have not left the supply floating.
     

  16. Prophetsnake

    Prophetsnake Tele-Meister

    134
    Aug 2, 2016
    ireland
    Thanks!
    You're correct. no fuse at the moment, but it won't be difficult to add one, of course. If I decide to keep this amp I will do so.
    I did re-use the two 100 Ohm resistors and earth them. So they are only floating in the sense that I haven't secured them anywhere yet.


    One odd thing I have noticed is that the voltage at TP12, which rises to 360DC with the tubes in and 384 with them out, dissipates almost immediately when the amp is shut down with the tubes in and has to be manually discharged when they are out. I don't see any natural reason for this. Is it some kind of safety circuit? By the way, this seems to be the main point where all of the residual voltage is indicated. If I discharge there, all other voltages are gone as well. Is this a reasonably safe assumption?

    Anyhow, this is what I am getting across the board with the tubes in. I'm reasonably certain that the OT is shot - no continuity through the primary.

    TP1 - .12 AC
    TP2 - 204 DC
    TP3 - 0
    TP4 - 0
    TP5 - 206 DC
    TP6 - 1.6 DC
    TP7 - 1.6 DC
    TP8 - 14 DC
    TP9 - MINUS 7.8 DC ? I don't get this at all.
    TP10 - 311 DC
    TP11- 336DC
    TP12 - 369DC
    TP13 - 0

    The rest are either defunct - due surgery - or as advertised.

    I'm assuming that the issue at TP9 is down to the OT failure? Or could there be a problem with the valve itself?
     

  17. Bendyha

    Bendyha Tele-Afflicted Ad Free Member

    Mar 26, 2014
    Northern Germany
    This is as to be expected, the charge in the capacitors is being discharged through the tubes. As your main B+ point you can discharge everything there.

    All other measurements read as expected.
    Except;

    TP9 will not recieve the full voltage if the OT Primary is shot, which it seems to be.

    The screen of the tube is still recieving a full charge at pin 4 from the TP11 source. This is cusing some current to flow through the tube which is what you are measuring at TP8, the cathode. This 14V is far below the voltage that will be measured when the plate is drawing current.
    The plate TP9 would normaly have a higher voltage than the screen, this being supplied through the OT.
    What is happening now is that the screen is drawing current away from the cathode (which is meant to do, but these would normally be attracted to the higher voltage plate in a beam, but the plate is not high voltage now, so the screen is atracting the electrons- which it is only meant to do in small amounts (it is a very thin wire, compared to the big grey plates of the anodes.) How electrons are freeing themselves from the plate to give you this negative reading, I am not too sure.....but the tube should not be powered up without a plate voltage.
    So, as to whether the tube is still good......we will be able to test that first when the new OT is installed...but if you run it with no plate voltage, it won't be good for long!
     

  18. Bendyha

    Bendyha Tele-Afflicted Ad Free Member

    Mar 26, 2014
    Northern Germany
    I should think that by the fact you are measuring the voltage on the plate, the multimeter is forming part of a circuit which alows the electrons shooting past the screen to find a way to find a route to ground, so if you don't measure the voltage, it isn't there.
     

  19. Prophetsnake

    Prophetsnake Tele-Meister

    134
    Aug 2, 2016
    ireland
    Sure, and if I understand the significance of that, it's that the primary on the OT must be good for that to happen, yes?
     
    Last edited: Jul 29, 2017

  20. Prophetsnake

    Prophetsnake Tele-Meister

    134
    Aug 2, 2016
    ireland
    New OT, and it works! Yay! It sounds good as well. Some noise at high volume, not a lot, but I'm putting that down to there being very little shielding at the moment. I'll sort that out.

    The new transformer is a Classic Tone.Prresumably this should sound better than the original Chinese unit.
    Speaker is a Celestion 8-15.

    Thanks so much for your help.
     
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