Rega Cartridge Impedance Help

[Bufo Bill]

At least I got that right.
Cheers, Bill.

[Radio Wrangler]

Originally Posted by Bufo Bill

David, what is the smoke bomb? Something I did? Will check meter tomorrow.

A Rifa capacitor soldered across the mains connections of the switch on the back of the volume control.

Those little gold capacitors hold a surprising amount of particularly foul-smelling smoke and their mission is to share it with you! They will wait for years for the right moment.

They were required to get things to pass the rf interference regs which came in in the 80's and Rifa was seen as the premium maker. Good hifi makers had been using them for some time. RF suppression stops the ingress of fridge clicks as well. Back in the day, I designed them into HP gear and thought I was doing well!

Little did any of us know.

David

[Bufo Bill]

Should I replace it?

[ms660]

Originally Posted by Bufo Bill

At least I got that right.
Cheers, Bill.

Check the HT from the power supply, it appears to have gone missing according to the voltage checks so far with both of your meters.

Lawrence.

[Bufo Bill]

Will work on it tomorrow Lawrence. Thanks for your help.

[PJL]

When channels are paralleled, L or R only signals will create a current in the opposing channel which will deflect the stylus. Not sure what effect that will have, maybe it doesn't matter.

[Radio Wrangler]

It will have the effect of making the cartridge slightly less compliant in the L-R difference direction, up/down. Lenz' law.

Given the winding impedances and the velocity to voltage coefficient of a typical cartridge, I think it's fairly slight.

Build a supeconducting cartridge with a hyper-strong magnet and the difference direction will be locked by paralleling the outputs making it a mono cartridge to the point of damaging stereo records!

David

[PJL]

That's the kind of thinking I had in mind. I wonder if it would be better to mix the outputs with a divider chain? 47K leaves plenty to play with.

[Bufo Bill]

I think I must be doing something wrong. When I attach my COM lead of my multimeter to the chassis and the red input terminal is on the wire coming from a resistor I get no continuity on my meter. When I measure voltage on the wire at either end of a resistor I get nothing. I can measure the resistance perfectly. When I put both leads on the chassis I get continuity. I cannot get continuity between cathode and chassis or anode and chassis. I can repeat these results exactly with my other multimeter. I think it would be very odd if both meters had the same fault, so maybe I've got this wrong? The voltage reads correctly on 9V battery on both meters.

[ms660]

Continuity is for checking conductor continuity between two points or something that would normally have a low resistance value, under normal conditions the resistance between that cathode and chassis is relatively high , so is the resistance between HT/anode circuit and chassis.

Lawrence.

[Bufo Bill]

Yes, sorry I was just using continuity to establish if I was open circuit or not, as the one meter has a buzzer for this. I used the Ohm setting for the resistors, and that works fine. Accurate on both meters. My concern was that the volt reading was broken somehow but it's exactly the same on both meters, they both get the same voltage strength on a 9v battery.

[ms660]

If both meters are working ok and neither show any HT then the HT is missing, if that's so then check back to the HT power supply, note: high voltages encountered in valve amps etc can be lethal.....as in electrocution.

Lawrence.

[Bufo Bill]

Hi, I've been having a think about this, and I've decided to bow out at this point. I think it's become obvious to us all that I don't have the skills needed to go on unaided, particularly as we are now dealing with dangerously high voltages. I don't want to be the untrained numpty who gets blown across the room by his amp. I have had Quad do some work in the past, I think I'll let them sort it out.
Thank you all for your help so far, I'll let you know the results of the work.
Cheers from Bill.

[Radio Wrangler]

None of us were born with any skills other than those needed to make bad smells and cry.

Skills are acquired.

You are in exactly the situation where a lot of learning goes on. Don't stop now or you'll miss out on the best educational bits. You don't have to continue unaided, there is plenty of aid available on here and people have the patience to get you past the difficulty. Missing HT sounds like a broken wire or an resistor gone very high, which is probably a fairly basic fault. High voltages are involved, so care is needed. Learning that care is like learning to swim, it's something that may save your life someday.

A broken connection or high resistor can be found with no power on, just using the ohms range on your meter. As a 13 year old I built an oscilloscope in my bedroom The CRT had mains-derived EHT from a 0Hz 2kV transformer and people on here will tell you how dangerous that is. I had no-one to guide me, I had to work everything out for myself. Somehow, I survived.

David

[Bufo Bill]

Hi David, thanks for your support. I'll go through the resistors one by one tomorrow. It seems very odd that the only problem I was aware of was some distortion on the phono output, the radio and even an attenuated signal from my laptop via DAC sounded perfect. Thus opening the unit up to find no HT makes me doubt myself and my abilities. I'll go through the resistors tomorrow.
Many thanks from Bill.

[Edward Huggins]

You have struggled long and hard wth this.
If you do return it to Quad, do let us know how their "legendary" service plays out....

[Bufo Bill]

I looked at some YouTube videos last night, and some seem to suggest that you need to unsolder one end of the resistor before testing. I would much like to hear from my friends here if this is the best way of testing? I have not been doing this up to now.
Thanks from Bill.

[ms660]

Yes, if you're unsure of how the circuit etc works then disconnect one end of the resistor to be measured is best, that eliminates any shunt resistance errors whether it be due to resistors or capacitors or anything else..

Lawrence

[Bufo Bill]

R16 measures 0.001 Ohm in circuit. Will unsolder one end and retry.

[Bufo Bill]

Dead as a dodo R16. Do I go through the rest now or repair one component at a time?