Dynatron Henley RG33W radiogram

[ms660]

Been trying to analyze that circuit in the last bunch of pictures, at first glance there seems to be something unconventional/advanced about it? I could be wrong, it's late for me, might have another look tomorrow.

Initially from what I can make out some of the grid coupling capacitors are disc ceramics, not the most reliable at that age.

Maybe some of the other forum members can reverse engineer a bit, it does seem unusual at first glance?

By the way was the rectifier in place when the grid voltage was measured?

Lawrence.

[peter_sol]

0 volts is good the ceramic caps don't need changing, just replace the electrolytics

[Vintage84]

No, the rectifier was out (as were all other valves).

I intend to spend some time dedicated to this over the bank holiday and will produce a diagram of the circuits so I can get a better understanding of what's actually going on in the "rats nest"!

I can't really justify spending a lot of money on outside help at the moment, so will have to keep reading up on how things work. The 2 LEMCO capacitors are the only ones which are particularly awkward to get to anyway.

[ms660]

Disc ceramics have been known to break down, tubular ceramics less so, it's not worth the risk with a nice unit of this vintage.

Some years ago I happened to come by a Hammarlund comms receiver, very nice too as you would expect from Hammarlund, I applied power via a variac (115volt receiver) it worked very well except that the xtal marker oscillator had packed up, that was an easy fix, 470k grid leak resistor open circuit, but latterly the receiver developed problems, leaking disc ceramics including screen grid decouplers and the audio output grid coupling capacitor, transformers got hot. Just sayin'

Replacement capacitors for the output grid couplers are cheap and readily available and not difficult to fit.

As has been said by others, other capacitors should be replaced, notably the black Lemco electrolytics and the red/yellow/black Plessey electrolytics and any Hunts brand types.

The HT reservoir and filter Can capacitor should also be checked, usually a visual inspection of it's can and base will suffice as a first step (Bulging can/bulging base, visual leakage of electrolyte etc.

For beginners, components are best replaced one at a time and the connections/workmanship should be fully checked before proceeding to the next, a quick sketch of the connections is a good idea before removal.

The only vintage grid couplers I would have any faith in would be the Mullard "Mustard" types and high quality PIO (Paper in oil) types.

If the OP wishes to continue then suspect capacitors should be identified, capacitance values and max voltage values noted, then ordered.

On the other hand, while waiting for components he could try refitting all the valves and powering it up as the primary fault (heater circuit short) appears to have been resolved, if the OP does this then the HT and control grids of the output valves should be monitored voltage wise, any sign of low or plummeting HT then switch off PDQ ditto if the control grids show a +ve reading.

The options for the OP powering up if he wishes to in the meantime are cave man style (plug in and be damned...T*ts up/Yay it works) or via a lamp limiter.

Lawrence

[ms660]

Whoops my post crossed with the OP's

Good man, only quit when you have to.

Lawrence.

[ms660]

To the OP and other folks that might be interested:

From what I can gather the Dynatron RG21 Henley uses a similar if not the same valve line up, here's a link to a page which has a thumbnail picture of an audio output stage schematic for the RG21:

https://www.vintage-radio.net/forum/...ad.php?t=44627

The triode of one of the ECL82's is the phase splitter (V6a in the schematic) the other triode being the preceding audio amp (V7a in the schematic)

There might or might not be some component value/circuit differences, I've posted this up for reference as it might help as a basis for the OP to trace the circuit/components in his unit.

Lawrence.

[peter_sol]

No good measuring voltages with the valves out.

[Vintage84]

Originally Posted by pwdrive

From what I can gather the Dynatron RG21 Henley uses a similar if not the same valve line up

I think there are some differences in the valve line up.

RG21 Henley: ECC85 ECH81 EBF89 ECC83 EM84 ECL82 ECL82 ECL82 ECL82
RG33 Henley: ECC85 ECH81(?) EBF89 ECC83 EZ81 EM84 ECL82 ECL82 ECL82 ECL82

I put a question mark by the ECH81 as I haven't been able to confirm the this one.

[ms660]

Yes, no valve rectifier in the RG21 so far as I understand, probably a selenium rectifier instead.

The ECH81 (Local oscillator/mixer) is almost certainly fitted in your unit.

Lawrence.

[ms660]

Also the RG21 is available as a download from this site for £1.99, cheap enough, it might help:

http://www.service-data.com/product....17/1833/a11317

Also listed is the RG33 Cliveden but in the thumbnail pic on the download page it appears to be the RG23, it might or might not cover your unit.

Maybe someone on here will know?

The RG33s listed is a transistorised job, you can ignore that one.

Lawrence.

[julie_m]

There aren't many other valves that would complete the RG33 line-up besides an ECH81, and the picture posted earlier by the OP certainly looks like an ECH81.

Before you put the valves back, you could try making the link from tag 1 to 4 with just one strand taken from a length of stranded wire. This will act as a primitive fuse, and enable you to take voltage measurements at each valve holder (note that the ECC83 has a slightly different heater wiring from all the other valves, and you need to measure from pin 4 to 9 and pin 5 to 9) but if the short-circuit comes back, the thin wire should fail before the transformer windings. If the set is OK after an hour or so like this, then fit a heftier link and replace the valves.

The capacitors going to pin 3 of each ECL82 are the most urgent to replace. Do one at a time, take plenty of pictures as you go and test the set in between doing each one and the next to be sure you connected it correctly.

[peter_sol]

I think we have established that those caps are ceramic and unlikely to need replacing, hence the measurement on the grids of ECL82's with the valves in.

[Station X]

Originally Posted by pwdrive

Also the RG21 is available as a download from this site for £1.99, cheap enough, it might help:

http://www.service-data.com/product....17/1833/a11317

Also listed is the RG33 Cliveden but in the thumbnail pic on the download page it appears to be the RG23, it might or might not cover your unit.

Maybe someone on here will know?

The RG33s listed is a transistorised job, you can ignore that one.

Lawrence.

We've been through this before earlier in the thread. As far as I can see the reference to an RG33 on VRSD is an error. The service sheet it points to does not cover that model.

The only source of a manual for the Dynatron Henley RG33W I could find online was this one:-

https://www.vintage-radio.net/forum/...2&postcount=17

[Edward Huggins]

As you're now at page 8 and with 154 postings, why not get some help? Edward

[Vintage84]

Apologies if this thread has been dragging on. It has been a steep learning curve, but think we've made some progress now.

I can't really justify the cost of the only help that has been offered on here and I assume any other repair shops would charge a similar figure.

[julie_m]

I don't think it's so bad that the thread has got long. Every question has been met with at least one response, and there were occasions -- it will be obvious from the timestamps -- where the pictures, suggested tests and measurement results were coming through pretty much in real-time. We have managed to establish that the transformer is undamaged, and that there was an intermittent short-circuit on the heater line somewhere; and we have a programme of tests to ensure the short is cleared and the DC blocking capacitors are O.K. I call that getting somewhere.

I'm wondering whether that wire link from tag 1 to 4 on the transformer might have originally been meant to serve as a crude fuse. I don't think it would do any harm to fit a proper fuseholder and fuse here, especially given that the transformer has already been a bit overstressed.

[ms660]

I agree, although several pages long it's now like resetting the calendar to year one, the fuse idea is sensible too.

Lawrence.