Help needed with Dynatron RG11 Berkeley - Page 3 - UK Vintage Radio Repair and Restoration Discussion Forum

B.Taylor · 29th Oct 2021, 10:31 pm

I thought the decks in these were fitted with Tannoy variable reluctance cartridges. If yours has this then the Expert stylus company can rebuild it and supply a suitable stereo compatible stylus.
Bill

HoverJohn · 30th Oct 2021, 9:24 am

Ah that’s good to know I need to work out how the head comes off I can see some screws under the plug to loosen. I have a few new stylus I found in his desk including an old mono one so it might have been compatible already?? Did they do that back in the day? If so how do I tell?

B.Taylor · 30th Oct 2021, 10:04 am

If it is the original deck (RC 88) the head shell just pulls off. Please post photo to confirm before forcing anything.

How do you know its mono? The styli for the Tannoy cartridge are just colour coded with dots of paint. Maybe you do not have this cartridge. Please post a photo of this too.

Bill

HoverJohn · 30th Oct 2021, 1:23 pm

I’ve got these 2 stylii too…..

Edward Huggins · 30th Oct 2021, 1:39 pm

Well this is the Tannoy Variable Reluctance ("Variluctance") Mono cartridge. Well regarded in its day. Just pull the head-shell off the tone arm. Now I see this, changing cartridge will not be so straightforward. This cartridge gives just 3.5mV output and fitting in a modern ceramic cartridge to replace it will dramatically overload the pre-amplifier stages of the Dynatron amplifier. Remember any 4 pin stereo cartridge fitted to this will need to have the RH and LH channels bridged on the cartridge itself as there are only 2 wires in the Garrard's tone arm.

B.Taylor · 30th Oct 2021, 2:13 pm

Yes that's the original Tannoy cartridge.

The stylus tip dimension must suit the records you are playing to avoid damage.

78's require a tip approx 2.5 mil wide ( a mil being one thousand of an inch )
Mono records approx 1 mil and stereo records approx 0.6 mil

The stylus marked LP may be for stereo but not sure. Other members may be able to advise.

If you decide to send the cartridge to be repaired they can check the stylus for you.

The whole headshell complete with cartridge should just pull off from the tone arm

thermalrunaway · 30th Oct 2021, 3:04 pm

Quote:

Originally Posted by B.Taylor

Yes that's the original Tannoy cartridge.

The stylus tip dimension must suit the records you are playing to avoid damage.

78's require a tip approx 2.5 mil wide ( a mil being one thousand of an inch )
Mono records approx 1 mil and stereo records approx 0.6 mil

The stylus marked LP may be for stereo but not sure. Other members may be able to advise.

If you decide to send the cartridge to be repaired they can check the stylus for you.

The whole headshell complete with cartridge should just pull off from the tone arm

Hi everyone,
unfortunately there is not enough vertical compliance in these for stereo, and the tip mass is quite high. Great little cartridge for 78s though. The output is much lower than a ceramic/crystal. You should be able to substitute an MM cartridge with the coils connected in series.
Rob.

thermalrunaway · 30th Oct 2021, 3:18 pm

Quote:

Originally Posted by Edward Huggins

Well this is the Tannoy Variable Reluctance ("Variluctance") Mono cartridge. Well regarded in its day. Just pull the head-shell off the tone arm. Now I see this, changing cartridge will not be so straightforward. This cartridge gives just 3.5mV output and fitting in a modern ceramic cartridge to replace it will dramatically overload the pre-amplifier stages of the Dynatron amplifier. Remember any 4 pin stereo cartridge fitted to this will need to have the RH and LH channels bridged on the cartridge itself as there are only 2 wires in the Garrard's tone arm.

Hi,
the Tannoy cartridge has the same 1/2" mount and 3/8" overhang as a modern MM cartridge. It outputs 10mV on LPs and 20mV on 78s. It tracks at 4g and the load is 47k. It is a licensed copy of the GE VR from America, which set the industry standard that persists to this day.
Rob.

HoverJohn · 1st Nov 2021, 10:45 am

So industrial standards of modern gram pickups were based in this unit - half a chance what I ordered will fit. Do I need to place a resistor in the circuit to protect the input valve if a modern cartridge is “stronger” than the tannoy variluctance unit?

Edward Huggins · 1st Nov 2021, 1:57 pm

We are still not sure what replacement cartridge you have now ordered?
If it is a Moving Magnet cartrridge such as a later version of the low-cost AT91, all should be well. But if it is a Ceramic stereo cartridge, then it will need careful attenuation by using a frequency compensating circuit and this will more than just a single series resistor.

HoverJohn · 1st Nov 2021, 10:14 pm

Ok here it is - just a cheap something to try… although it’s 200-300mv so could be too much.
https://www.ebay.co.uk/itm/Stereo-Ca...-127635-2958-0
I prepare for you judgement on my foolish purchase…..

However could it be that the original pickup didn’t provide enough output for the amp I texted it on??

Edward Huggins · 2nd Nov 2021, 8:50 am

It's not really a "foolish purchase as the cartridge you have ordered can really give a surprisngly good sound. The issue is to now ensure a correct matching to the Dynatron's gram input stage.

Herald1360 · 2nd Nov 2021, 10:42 am

You may not be as badly off with your ceramic cartridge as you think..... its recommended load will be in the Megohm region. The 47k load for the Tannoy original should do a reasonable job of selectively attenuating the ceramic output to something not a million miles away from the Variluctance's level. If not, a few Rs and Cs would probably sort it.

A discussion of this very issue is here:

https://www.vintage-radio.net/forum/...d.php?p=300251

Also see attached:

HoverJohn · 2nd Nov 2021, 3:49 pm

Cool I’m gonna read that later. I wonder if I can mount it and leave the variluctance selector mounted with a “hockey leg” to flip the needle… although it’s a lot of weight.

Edward Huggins · 2nd Nov 2021, 5:20 pm

No, regret not. The stylus in the ceramic cartridge "flips" over and the cartridge remains fixed in-situ, whereas with the Tannoy, the whole cartridge, with its 2 styli, "turns" over.

HoverJohn · 2nd Nov 2021, 10:35 pm

Ok I read all that and some of it tally’s with my engineering knowledge but some of it is all foreign to me! Here’s my wiring diagram as that may help, also how does the suggestion of placing the 2 stereo output in series instead of parallel?? Would that make the output voltages higher or would the increased impedance help??

JB

HoverJohn · 3rd Nov 2021, 10:28 pm

So today my cheap megger arrived - it seems to make the voltages claimed (albeit polarity reversed !) and correctly identified the 10M resistance in my multimeter. I’ve started testing caps at 250v (they run at 75 but rated at 450) and some of the hunts ones are in the 8Mohms region but one of the big smoothing caps is 1.1meg at 250 but only 156k at 300v (I assumed it was dodgy so tried 500v but the limited current of the megger shows it breaking at 300v) the paper waxy thing is down at 100k so as predicted by you guys it’s dead.

Glad I hooked up the volt meter as the caps take a while to dissipate!!

So what is acceptable resistance? Also the big one that broke down at 300v seemed to be reforming at 250 as the resistance was increasing? (Operates at 185v ) is that an acceptable position on a power smoothing cap?

Advice welcome.

HoverJohn · 6th Nov 2021, 9:09 am

Ok so I’m reasonably set to start changing the dead bits one by one but I’m still not sure how to match the new ceramic pickup to the amp? …

Edward Huggins · 6th Nov 2021, 11:50 am

Re-read the advice already offered as to ceramic cartridge matiching. Have you installed the new cartridge yet? Do check its tracking angle as advised. If it is oveloading the ampifier you will hear early-onset distortion. Also if the impedence matching is not as it needs to be, the sound will be thin with liitle bass.

HoverJohn · 6th Nov 2021, 3:55 pm

Ok I will read again - I just didn’t understand all of it. Is it lazy to consider a 0-500meg log variable resistor for this or will it pick up too much noise? It’s not installed yet - I have a long way to go before that as I haven’t started the pre amp and power amp yet, I just like to plan ahead and I’m not great with things I don’t understand.

Although I did get the head shell off and the old pickup removed it was all very corroded.

29th Oct 2021, 10:31 pm	#41
B.Taylor Tetrode Join Date: Feb 2020 Location: Cheltenham, Gloucestershire, UK. Posts: 82	Re: Help needed with Dynatron RG11 Berkeley I thought the decks in these were fitted with Tannoy variable reluctance cartridges. If yours has this then the Expert stylus company can rebuild it and supply a suitable stereo compatible stylus. Bill

30th Oct 2021, 9:24 am	#42
HoverJohn Pentode Join Date: Oct 2021 Location: Newbury, Berkshire, UK. Posts: 132	Re: Help needed with Dynatron RG11 Berkeley Ah that’s good to know I need to work out how the head comes off I can see some screws under the plug to loosen. I have a few new stylus I found in his desk including an old mono one so it might have been compatible already?? Did they do that back in the day? If so how do I tell?

30th Oct 2021, 10:04 am	#43
B.Taylor Tetrode Join Date: Feb 2020 Location: Cheltenham, Gloucestershire, UK. Posts: 82	Re: Help needed with Dynatron RG11 Berkeley If it is the original deck (RC 88) the head shell just pulls off. Please post photo to confirm before forcing anything. How do you know its mono? The styli for the Tannoy cartridge are just colour coded with dots of paint. Maybe you do not have this cartridge. Please post a photo of this too. Bill

30th Oct 2021, 1:23 pm	#44
HoverJohn Pentode Join Date: Oct 2021 Location: Newbury, Berkshire, UK. Posts: 132	Re: Help needed with Dynatron RG11 Berkeley I’ve got these 2 stylii too….. Attached Thumbnails

30th Oct 2021, 1:39 pm	#45
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,335	Re: Help needed with Dynatron RG11 Berkeley Well this is the Tannoy Variable Reluctance ("Variluctance") Mono cartridge. Well regarded in its day. Just pull the head-shell off the tone arm. Now I see this, changing cartridge will not be so straightforward. This cartridge gives just 3.5mV output and fitting in a modern ceramic cartridge to replace it will dramatically overload the pre-amplifier stages of the Dynatron amplifier. Remember any 4 pin stereo cartridge fitted to this will need to have the RH and LH channels bridged on the cartridge itself as there are only 2 wires in the Garrard's tone arm. __________________ Edward.

30th Oct 2021, 2:13 pm	#46
B.Taylor Tetrode Join Date: Feb 2020 Location: Cheltenham, Gloucestershire, UK. Posts: 82	Re: Help needed with Dynatron RG11 Berkeley Yes that's the original Tannoy cartridge. The stylus tip dimension must suit the records you are playing to avoid damage. 78's require a tip approx 2.5 mil wide ( a mil being one thousand of an inch ) Mono records approx 1 mil and stereo records approx 0.6 mil The stylus marked LP may be for stereo but not sure. Other members may be able to advise. If you decide to send the cartridge to be repaired they can check the stylus for you. The whole headshell complete with cartridge should just pull off from the tone arm

1st Nov 2021, 10:45 am	#49
HoverJohn Pentode Join Date: Oct 2021 Location: Newbury, Berkshire, UK. Posts: 132	Re: Help needed with Dynatron RG11 Berkeley So industrial standards of modern gram pickups were based in this unit - half a chance what I ordered will fit. Do I need to place a resistor in the circuit to protect the input valve if a modern cartridge is “stronger” than the tannoy variluctance unit?

1st Nov 2021, 1:57 pm	#50
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,335	Re: Help needed with Dynatron RG11 Berkeley We are still not sure what replacement cartridge you have now ordered? If it is a Moving Magnet cartrridge such as a later version of the low-cost AT91, all should be well. But if it is a Ceramic stereo cartridge, then it will need careful attenuation by using a frequency compensating circuit and this will more than just a single series resistor. __________________ Edward.

1st Nov 2021, 10:14 pm	#51
HoverJohn Pentode Join Date: Oct 2021 Location: Newbury, Berkshire, UK. Posts: 132	Re: Help needed with Dynatron RG11 Berkeley Ok here it is - just a cheap something to try… although it’s 200-300mv so could be too much. https://www.ebay.co.uk/itm/Stereo-Ca...-127635-2958-0 I prepare for you judgement on my foolish purchase….. However could it be that the original pickup didn’t provide enough output for the amp I texted it on?? Last edited by HoverJohn; 1st Nov 2021 at 10:24 pm.

2nd Nov 2021, 8:50 am	#52
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,335	Re: Help needed with Dynatron RG11 Berkeley It's not really a "foolish purchase as the cartridge you have ordered can really give a surprisngly good sound. The issue is to now ensure a correct matching to the Dynatron's gram input stage. __________________ Edward.

2nd Nov 2021, 3:49 pm	#54
HoverJohn Pentode Join Date: Oct 2021 Location: Newbury, Berkshire, UK. Posts: 132	Re: Help needed with Dynatron RG11 Berkeley Cool I’m gonna read that later. I wonder if I can mount it and leave the variluctance selector mounted with a “hockey leg” to flip the needle… although it’s a lot of weight.

2nd Nov 2021, 5:20 pm	#55
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,335	Re: Help needed with Dynatron RG11 Berkeley No, regret not. The stylus in the ceramic cartridge "flips" over and the cartridge remains fixed in-situ, whereas with the Tannoy, the whole cartridge, with its 2 styli, "turns" over. __________________ Edward.

2nd Nov 2021, 10:35 pm	#56
HoverJohn Pentode Join Date: Oct 2021 Location: Newbury, Berkshire, UK. Posts: 132	Re: Help needed with Dynatron RG11 Berkeley Ok I read all that and some of it tally’s with my engineering knowledge but some of it is all foreign to me! Here’s my wiring diagram as that may help, also how does the suggestion of placing the 2 stereo output in series instead of parallel?? Would that make the output voltages higher or would the increased impedance help?? JB Attached Thumbnails

3rd Nov 2021, 10:28 pm	#57
HoverJohn Pentode Join Date: Oct 2021 Location: Newbury, Berkshire, UK. Posts: 132	Re: Help needed with Dynatron RG11 Berkeley So today my cheap megger arrived - it seems to make the voltages claimed (albeit polarity reversed !) and correctly identified the 10M resistance in my multimeter. I’ve started testing caps at 250v (they run at 75 but rated at 450) and some of the hunts ones are in the 8Mohms region but one of the big smoothing caps is 1.1meg at 250 but only 156k at 300v (I assumed it was dodgy so tried 500v but the limited current of the megger shows it breaking at 300v) the paper waxy thing is down at 100k so as predicted by you guys it’s dead. Glad I hooked up the volt meter as the caps take a while to dissipate!! So what is acceptable resistance? Also the big one that broke down at 300v seemed to be reforming at 250 as the resistance was increasing? (Operates at 185v ) is that an acceptable position on a power smoothing cap? Advice welcome. Attached Thumbnails

6th Nov 2021, 9:09 am	#58
HoverJohn Pentode Join Date: Oct 2021 Location: Newbury, Berkshire, UK. Posts: 132	Re: Help needed with Dynatron RG11 Berkeley Ok so I’m reasonably set to start changing the dead bits one by one but I’m still not sure how to match the new ceramic pickup to the amp? …

6th Nov 2021, 11:50 am	#59
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,335	Re: Help needed with Dynatron RG11 Berkeley Re-read the advice already offered as to ceramic cartridge matiching. Have you installed the new cartridge yet? Do check its tracking angle as advised. If it is oveloading the ampifier you will hear early-onset distortion. Also if the impedence matching is not as it needs to be, the sound will be thin with liitle bass. __________________ Edward.

6th Nov 2021, 3:55 pm	#60
HoverJohn Pentode Join Date: Oct 2021 Location: Newbury, Berkshire, UK. Posts: 132	Re: Help needed with Dynatron RG11 Berkeley Ok I will read again - I just didn’t understand all of it. Is it lazy to consider a 0-500meg log variable resistor for this or will it pick up too much noise? It’s not installed yet - I have a long way to go before that as I haven’t started the pre amp and power amp yet, I just like to plan ahead and I’m not great with things I don’t understand. Although I did get the head shell off and the old pickup removed it was all very corroded.