Dansette Conquest Auto

[ms660]

-ve on the rectifier is AC in, +ve is +DC out.

EDIT: Post crossed.

Lawrence.

[DonaldStott]

Originally Posted by Station X

You need to measure the DC HT voltage across the reservoir and smoothing capacitors.

I'm measuring 255V, 162V and 10V respectively on the reservoir and smoothing capacitors.

Looks like I need to unbolt the mains transformer to get at the valve pins and the main board?

[Station X]

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.

[ms660]

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.

[Station X]

Yup. That circuit even quotes voltages.

There's a fourth electrolytic cap which should have 1 Volt DC across it.

[crackle]

Is that a mustard cap on the circuit board? If it is then it won't need to be changed.

Mike

[DonaldStott]

Originally Posted by ms660

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.

Thanks Lawrence for that information and the link.

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.

Originally Posted by crackle

Is that a mustard cap on the circuit board? If it is then it won't need to be changed.

Normally I would agree Mike but it is the 0.01μF audio coupling capacitor!

At this stage though I'm minded not to replace anything although ...

Originally Posted by Station X

There's a fourth electrolytic cap which should have 1 Volt DC across it.

I may be measuring this incorrectly but across that blue electrolytic I'm only getting 0.18V DC??

[ms660]

Originally Posted by DonaldStott

Thanks Lawrence for that information and the link.

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.

The values shown in the Monarch schematic are the same and clearer, I posted the link to the MKII schematic to show that there was indeed a MKII version....whicheverways I'll do a component ID list and I'll post it up in a bit.

Lawrence.

[Station X]

Originally Posted by DonaldStott

I may be measuring this incorrectly but across that blue electrolytic I'm only getting 0.18V DC??

Check the 2.2k cathode resistor and 220k anode resistor of the triode section.

[DonaldStott]

Originally Posted by DonaldStott

I may be measuring this incorrectly but across that blue electrolytic I'm only getting 0.18V DC??

I'm measuring between the +ve end of the blue electrolytic and ground/chassis?

[Station X]

That's the correct way of measuring. "Across" amounts to the same thing.

[DonaldStott]

Originally Posted by Station X

Check the 2.2k cathode resistor and 220k anode resistor of the triode section.

The 2.2k cathode resistor is measuring 2.31kΩ

The 220k anode resistor is measuring 1.85MΩ - WOW!

[ms660]

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.

[Station X]

Originally Posted by DonaldStott

The 2.2k cathode resistor is measuring 2.31kΩ

The 220k anode resistor is measuring 1.85MΩ - WOW!

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.

[DonaldStott]

Originally Posted by ms660

Dansette Conquest Auto MKII (also Monarch) component values as per the manufactures schematic:

Any errors then guilty as charged.

Thanks Lawrence, much appreciated.

[DonaldStott]

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?

[Station X]

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.

[DonaldStott]

Originally Posted by Station X

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.

Thanks Graham, you just have ... subject to the test below of course!

Originally Posted by Station X

Make sure there's no positive voltage on the control grid of the ECL82's pentode section.

Will do.

[DonaldStott]

Originally Posted by ms660

Dansette Conquest Auto MKII (also Monarch) component values as per the manufactures schematic:

I'm 95% of the way through updating the text on the manufactures schematic to make things clearer - thanks to Lawrence for the figures in Post #33 above.

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.

[Station X]

It's 1.0V above R5.