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Old 18th Oct 2021, 3:22 pm   #1
HoverJohn
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Question Help needed with Dynatron RG11 Berkeley

Hello, I’m new here, I just inherited my grandfathers dynatron Berkeley RG11 radiogram. However it’s not working well I can only get a faint radio sound (lots of knob crackle) and nothing from the Gram. Does anyone have any suggestions or advice or diagrams ? It’s got the mono ether pathfinder tuner T10A with a TC10A pre amp and LF10A amp and Garard gram.

It did work fine a couple of years ago until I removed all the fluff with a light brush and hoover. (I was worried my uncle was going to burn the house down with it…)

Short of changing all the valves and caps I’d not know where to look (appart from giving it all a wiggle)

All help greatly appreciated.

JB
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Old 18th Oct 2021, 8:01 pm   #2
Edward Huggins
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Default Re: Help needed with Dynatron RG11 Berkeley

This is a big complex beast of a Radiogram, You give the impression that you have little or no experience of working with vintage electronics - and with this you'll not get a harder project.....if I'm wrong then please forgive me. What are your plans for this, a full restoration or just to, say, get it play records?
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Old 18th Oct 2021, 9:01 pm   #3
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Default Re: Help needed with Dynatron RG11 Berkeley

It’s in my somewhat retro office and I’m aiming for it to be my daily tunes. Yes it is my first vintage electronics but I’m fairly handy with a soldering iron I’m aiming to keep it 100% original but with the one removable addition of a blue tooth module fed into the spare AF input. I’m looking to give its basic overhaul get it sounding good and enjoy it. I've built a Nixie tube clock soldering it all together which was quite fiddly. However I’ve been looking forward to fixing this for decades.
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Old 18th Oct 2021, 9:29 pm   #4
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Default Re: Help needed with Dynatron RG11 Berkeley

Useful information regarding repairing radios here. Equally relevant to radiograms:-

https://www.vintage-radio.com/repair...ion/index.html
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Old 18th Oct 2021, 9:47 pm   #5
John Caswell
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Default Re: Help needed with Dynatron RG11 Berkeley

The TC10A , LF10 etc are fairly standard preamplifier /amplifier units, but the T10A tuner is a much more complicated unit requiring specialised skills.
I have done a fair amount of work on Dynatrons of this vintage and may be able to help.
PM me with a phone nr and I will see what I can do

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Old 19th Oct 2021, 8:51 am   #6
Edward Huggins
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Default Re: Help needed with Dynatron RG11 Berkeley

If you do wish to keep this as near as possible 100% original, but do also wish to play records, do not attempt play Stereo LPs on this until you change the cartridge in the Garrard autochanger.
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Old 19th Oct 2021, 11:15 am   #7
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Default Re: Help needed with Dynatron RG11 Berkeley

John I will message you but looking forward to the fiddly bits do you have any amp or pre amp schematics? Looking to start there first as the tuner “works…”

Edward why do I need to fit a stereo needle? And would I wire the 2 outputs together to feed the pre amp?

Thanks, JB.
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Old 19th Oct 2021, 11:58 am   #8
Edward Huggins
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Default Re: Help needed with Dynatron RG11 Berkeley

Not, a Stereo "Needle" - but a replacement Stereo cartridge.
The one in the Garrard autochanger (assuming it is the orginal RC80) is for use with Mono records only and will damage Stereo LPs - and most LPs will be in Stereo. Yes, you will need to bridge the RH and LH channels on the new cartridge to suit your Mono pre-amp. But we can come to that later as and when you get the amplifier running.
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Old 20th Oct 2021, 9:13 am   #9
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Default Re: Help needed with Dynatron RG11 Berkeley

Hi so question on capacitors! I’m not too fussed about any hums at the moment but I want to ensure that a faulty cap won’t do any damage to the other components? Which ones do I need to swap out. Just the grid couplers? One big one is proving hard to find here’s a 50s mag advert for it on page 4 (530)

https://worldradiohistory.com/UK/Pra...on-1956-07.pdf

If critical I need a ce60pe replacement (actually pictured) - although the capacitor page on the link I was given previously stated the TCC stuff as fairly tough? And looking at the 29 shillings a piece must have been half decent in the day…

Unit made no hums when on previously…


JB
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Old 20th Oct 2021, 12:25 pm   #10
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Default Re: Help needed with Dynatron RG11 Berkeley

Don't leave this powered up for long as faulty grid coupling capacitors can result in expensive damage to the output and mains transformers. Even a very slight leakage in these capacitors will cause the output valves to run at very high current. Post a picture of the underside and we can point the critical capacitors out. Hum is a symptom of faulty grid coupling capacitors.
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Old 20th Oct 2021, 2:02 pm   #11
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Default Re: Help needed with Dynatron RG11 Berkeley

The grid coupler is known as "that capacitor" in some quarters John and possibly by much stronger language if the worst happens. As PJL says a component costing very little can remove any possibility of a disastrous cascade leading to progressive damage. That's a great [1956] RG you've got there. Much later Dynatron models always seem a bit "over fussy" to me but this is a "high end", sturdy and the familiar cabinet design was also used by some other manufacturers. The T10 Ether Tuner is impressive in it's own right [8 valves and five wavebands covering early VHF transmissions!] The SW band starting at 2 Megs, would have been handy to tweak for the amateur [Top] Band 160 metres in those days but it's unlikely that anyone who could afford this Radiogram would want to mess with it I suppose!

Dave W

Last edited by dave walsh; 20th Oct 2021 at 2:29 pm.
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Old 20th Oct 2021, 2:24 pm   #12
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Default Re: Help needed with Dynatron RG11 Berkeley

Like I said John PM/email me with a phone Nr.
I have an Edinburgh full manual that I can scan for you which has similar/identical items in it. Don't, whatever you do, delve in mob handed.

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Old 20th Oct 2021, 3:17 pm   #13
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Default Re: Help needed with Dynatron RG11 Berkeley

Pics- most seem to be the allegedly more robust metal ones. One waxy thing
I can find a full set of valves for not much money but not sure which ones are reputable.
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Old 20th Oct 2021, 5:53 pm   #14
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Default Re: Help needed with Dynatron RG11 Berkeley

We could do with a picture of the underside but showing the valve bases that are hidden by the tag strip.

The two metalpac capacitors in parallel are probably the grid coupling capacitors and should be automatically replaced. There are two other capacitors, one metal attached to the chassis and one cardboard on the tag strip both of which I would recommend replacing. There maybe other capacitors on the back of the tag strip.

The carbon resistors used in the amplifier are notorious for changing value with age so if you want to use this regularly I would also recommend a full 'health check' which involves checking the value of every resistor and replacing if out of tolerance (you may need to unsolder one end of the resistor to get an accurate reading).

There are no 'robust' vintage capacitors above about 0.001uF as they are all based on oil impregnated paper and are prone to leakage, some can be left if they are in parts of the circuit where a little leakage would not matter.

Not having a circuit diagram is an issue as mistakes made during the restoration will be more difficult to track down. Taking lots of pictures and replacing parts one at a time and checking with the pictures becomes essential.

Valves are usually OK so do not order replacements yet.

Last edited by PJL; 20th Oct 2021 at 6:00 pm.
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Old 20th Oct 2021, 8:21 pm   #15
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Default Re: Help needed with Dynatron RG11 Berkeley

Probably worth saying it was working well with no issues and I think the problem is with the pre amp stages. No buzz or humming at all.
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Old 21st Oct 2021, 12:34 pm   #16
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Default Re: Help needed with Dynatron RG11 Berkeley

Ok picture update - here’s the extra one as requested showing the sockets and the pre amp which is where I think the issue is - the valves in here are mismatched and a few paper caps all original caps 🤨…
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Old 21st Oct 2021, 1:49 pm   #17
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Default Re: Help needed with Dynatron RG11 Berkeley

I can't see any paper caps in the first preamp picture but there are some metalpac ones partially showing in the picture of the valves, the little red ones are ceramic and normally reliable although hardly hi-fi quality.

Faulty capacitors in the preamp are unlikely to do much damage but those output valve grid coupling capacitors definitely will. There are many many threads on this forum with damaged transformers from leaking grid coupling capacitors both radio and power amplifiers.

If you want this equipment to work reliably and as the designer intended then it needs a full service. It won't cost much except in patience and time.
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Old 21st Oct 2021, 3:58 pm   #18
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Default Re: Help needed with Dynatron RG11 Berkeley

It didn’t seem to upload all the pics - 2nd attempt… there is a leaky paper one. You can see the wet bits on the board. So is the advice to replace All capacitors? If so which brands or quality do I need as I know the replacement won’t last this long!!
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Old 21st Oct 2021, 4:51 pm   #19
Edward Huggins
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Default Re: Help needed with Dynatron RG11 Berkeley

What ever you do, do not replace ALL the capacitors. These need to be changed, where needed, stage by stage.
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Old 21st Oct 2021, 9:45 pm   #20
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Default Re: Help needed with Dynatron RG11 Berkeley

Ok sounds promising as I’d like to keep it as original as possible but how do I tell what needs culling? I can’t risk blowing the transformers - although the main power amp does have 3 small trip units built in which gives me some wiggle room…
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