25th Nov 2019, 12:16 pm | #21 |
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Re: Dansette Conquest Auto
-ve on the rectifier is AC in, +ve is +DC out.
EDIT: Post crossed. Lawrence. |
25th Nov 2019, 12:52 pm | #22 | |
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Re: Dansette Conquest Auto
Quote:
Looks like I need to unbolt the mains transformer to get at the valve pins and the main board?
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25th Nov 2019, 12:55 pm | #23 |
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Re: Dansette Conquest Auto
I'd say those readings were OK. The first is the reservoir cap voltage, the second the smoothing cap voltage and the third will be the voltage on the cathode of the output valve, which will be the same as the grid bias.
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25th Nov 2019, 1:12 pm | #24 |
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Re: Dansette Conquest Auto
Just to note, the component values look similar to those used in the Monarch, which suggests that it's a Conquest Auto MKII, eg: it's not the D/T amplifier that's listed for the Conquest Auto in the R&TV servicing books.
The Conquest Auto MKII schematic can be found in the instruction book here: https://elektrotanya.com/dansette_pr...wnload.html#dl Lawrence. Last edited by ms660; 25th Nov 2019 at 1:29 pm. Reason: addition and link |
25th Nov 2019, 1:27 pm | #25 |
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Re: Dansette Conquest Auto
Yup. That circuit even quotes voltages.
There's a fourth electrolytic cap which should have 1 Volt DC across it.
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25th Nov 2019, 1:54 pm | #26 |
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Re: Dansette Conquest Auto
Is that a mustard cap on the circuit board? If it is then it won't need to be changed.
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25th Nov 2019, 3:09 pm | #27 | ||
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Re: Dansette Conquest Auto
Quote:
I've downloaded the schematic - I know it's free but a better scan would really have helped as I'm struggling to read some of the values. Quote:
At this stage though I'm minded not to replace anything although ... I may be measuring this incorrectly but across that blue electrolytic I'm only getting 0.18V DC??
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25th Nov 2019, 3:21 pm | #28 | |
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Re: Dansette Conquest Auto
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Lawrence. |
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25th Nov 2019, 3:29 pm | #29 |
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Re: Dansette Conquest Auto
Check the 2.2k cathode resistor and 220k anode resistor of the triode section.
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25th Nov 2019, 3:36 pm | #31 |
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Re: Dansette Conquest Auto
That's the correct way of measuring. "Across" amounts to the same thing.
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25th Nov 2019, 3:45 pm | #32 | |
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Re: Dansette Conquest Auto
Quote:
The 220k anode resistor is measuring 1.85MΩ - WOW!
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25th Nov 2019, 3:47 pm | #33 |
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Re: Dansette Conquest Auto
Dansette Conquest Auto MKII (also Monarch) component values as per the manufactures schematic:
VR1...1 meg VR2...1 meg VR3...250k R1...330k R2...56k R3...22K R4...56 ohms R5...2.2k R6...220k R7...680 ohms R8...680k R9...56k R10...18k R11...390 ohms C1...200pF C2...200pF C3...64uF C4...0.01uF C5...32uF C6...25uF C7...32uF Any errors then guilty as charged. Lawrence. |
25th Nov 2019, 3:51 pm | #34 |
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Re: Dansette Conquest Auto
High value resistors have a habit of drifting even higher. This high value resistor could well be the cause of the low voltage across the blue electrolytic cap.
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26th Nov 2019, 12:01 pm | #36 |
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Re: Dansette Conquest Auto
I have five resistors that are measuring more than 20% over their stated value and will be replaced.
I never know what type of resistor to choose for restoration projects and which is right for this type of project - metal film, metal oxide or carbon film? I do favour 2W resistors due to their size which don't look too out of place in vintage equipment? And what about that mustard cap - what's the consensus given that it is the audio coupling capacitor! For peace of mind I'd be inclined to replace it?
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26th Nov 2019, 5:39 pm | #37 |
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Re: Dansette Conquest Auto
I use 2W flameproof resistors for valve gear, but everyone has their own preferences.
Mullard Mustard capacitors have a very good reputation for reliability. I've never found a faulty one. If you're determined to change it though, nothing I can say will stop you. Make sure there's no positive voltage on the control grid of the ECL82's pentode section.
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26th Nov 2019, 6:20 pm | #38 | |
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Re: Dansette Conquest Auto
Quote:
Will do.
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26th Nov 2019, 10:01 pm | #39 | |
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Re: Dansette Conquest Auto
Quote:
Having a bit of difficulty with some of the voltage figures although so far I have ascertained 56V just above V.R.2., 10V just above R5 and 10V just above R11. Can't really make out the main voltage coming out of T.2, the voltage and amps to the left of the FC.116 and the voltage to the left of R10 - don't want to guess for obvious reasons. I'll Post the updated schematic as a PDF once it is complete.
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26th Nov 2019, 10:12 pm | #40 |
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Re: Dansette Conquest Auto
It's 1.0V above R5.
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