17th Dec 2014, 3:37 pm | #41 |
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Re: WEM Copicat Custom
I think the next thing for you to do is to take DC voltage readings from each valve pin to chassis (with the unit switched on of course) and post the readings here for analysis.
No need to do the heater pins, assuming of course that all the valves are lighting up. You could also measure all resistors (with power off of course) expect some strange readings though as some resistors are shunted by others.
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17th Dec 2014, 3:42 pm | #42 |
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Re: WEM Copicat Custom
Hi
Just fixed one of these with no replay output and the fault was due to a small Hunts capacitor (of course!) hidden by the larger electrolytics and also the coupling capacitor to the swell control being open. Glyn |
17th Dec 2014, 4:04 pm | #43 |
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Re: WEM Copicat Custom
@Station X ok will do and get back to you with the readings.
@Welsh Anorak congrats on getting yours working, not sure which caps you mean though, could you point them out on here? The one I replaced was a small cap almost behind the largest one, C9, possibly the same one? http://www.vintagehofner.co.uk/brita...opicatmk3.html |
17th Dec 2014, 4:52 pm | #44 |
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Re: WEM Copicat Custom
Here are the readings for the 3 valves, as numbered in the attached photo, which I think is the same pinouts as on the datasheet.
A: ECC83 1 =46v ANODE 2 = 0v GRID 3 = 0.34v CATHODE (4,5 = heater) 6 = going between plus and minus 0.1v ANODE 7 = 0v GRID 8 = 0.33v CATHODE (9 = heater) B: ECC83 1 = 57v ANODE 2 = 0v GRID 3 = 0v CATHODE (4,5 = heater) 6 = 48.5v ANODE 7 = 0v GRID 8 = 0.6v CATHODE (9 = heater). C: ECC83 1 = 77.5v ANODE 2 = -4.1v GRID 3 = 0v CATHODE (4,5 = heater) 6 = 47.2v ANODE 7 = -0.2v GRID 8 = 0.41v CATHODE (9 = heater) I haven't measured all the resistors yet, but R1 and R2 (input resistors) are zero ohms, not sure this is right... |
17th Dec 2014, 5:10 pm | #45 |
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Re: WEM Copicat Custom
R1 and R2 measure zero because they are short-circuited by the contacts of the input jacks. You'll need to insert an otherwise disconnected plug into the jack to get a true reading.
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17th Dec 2014, 5:15 pm | #46 |
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Re: WEM Copicat Custom
Can you check the HT voltages by measuring the DC Volts across C13 and C14 please.
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17th Dec 2014, 5:32 pm | #47 |
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Re: WEM Copicat Custom
Got a huge spark when i tried! Is it better to crocodile clip the meter probes to the caps and then plug it in? My cheap meter says 500v max, 10A, hope it wont blow...
Oh yes sorry, ok R1 and R2 are around 1 meg. R3 R4 and R5 are as they should be. R6 is 270k, R7 is 410 k...thats as far as I got |
17th Dec 2014, 5:37 pm | #48 |
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Re: WEM Copicat Custom
On a preliminary glance, you readings are well below those expected. Measuring the HT voltages may throw some light on this.
The valve you call 'A' is V1. Pins 1 and 6 should have similar voltages. Suspect a bad contact between the valve pins and the holder, or open circuit R5.
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17th Dec 2014, 5:39 pm | #49 |
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Re: WEM Copicat Custom
You are starting to frighten me!
I think you need to learn how to use your multimeter properly before you go any further! DON'T use the 10 amp range - or ANY other amp ranges to make voltage checks! High voltage ranges ONLY - and work down to lower ranges if needed. |
17th Dec 2014, 5:42 pm | #50 |
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Re: WEM Copicat Custom
There is no way you should get a huge spark with a meter on a VOLTS range. That is so long as you don't short-circuit something with your probe. Standard practice is to croc clip the negative lead to chassis (also the negative side of the smoothers) and probe any points to be measured with the positive lead.
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17th Dec 2014, 5:42 pm | #51 |
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Re: WEM Copicat Custom
Use 500 volt range and croc clip black negative lead to chassis and take voltage readings with the red probe lead - taking great care not to let it slip!
Edit: post crossed with Graham again. |
17th Dec 2014, 5:51 pm | #52 |
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Re: WEM Copicat Custom
Another strange thing is that V2, which I assume is the valve you call 'B', should have the full HT voltage on pin 2. We know it was there because it was being short-circuited by C9 which you replaced. Now it seems to have gone!
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17th Dec 2014, 5:52 pm | #53 |
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Re: WEM Copicat Custom
Oops yes, ok got it, sorry!
Across both caps (from either side of R27 and the negative wire from the transformer) its the same, about 790v |
17th Dec 2014, 6:06 pm | #54 |
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Re: WEM Copicat Custom
Ok I just swapped V1 for another one and now I'm getting 50v on pin 1 and 31v on pin 6.
Nothing at all on V2 pin 2 |
17th Dec 2014, 6:07 pm | #55 |
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Re: WEM Copicat Custom
You can't have 790 volts, that's far too high!
I'm wondering whether you've 'popped' your meter with that spark on the wrong range. |
17th Dec 2014, 6:07 pm | #56 | |
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Re: WEM Copicat Custom
Quote:
Can you post a picture of what you're doing please. Why does your picture show four croc clips?
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17th Dec 2014, 6:09 pm | #57 |
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Re: WEM Copicat Custom
I'll leave this to Techman for the moment if he doesn't mind. I have another job to do here.
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17th Dec 2014, 6:09 pm | #58 |
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Re: WEM Copicat Custom
You need to check your meter is reading correctly on a 'known' voltage before you go any further - a 9 volt battery will do to start with.
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17th Dec 2014, 6:11 pm | #59 |
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Re: WEM Copicat Custom
Yes, sorry Graham, I seem to keep crossing posts with you.
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17th Dec 2014, 6:17 pm | #60 |
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Re: WEM Copicat Custom
Let us know when you've checked your meter.
You should expect HT voltage readings over 200 volts at the smoothing capacitors, but below 300 volts. |