Regentone

[Radio Tech]

Hi Folks

Can someone identify this set, there does not appear to be a model number or even a serial number, I think it may be the later version of the 358 but cannot be certain. Here are a couple of pictures one of the front and one of the interior.

Regards

Ken

[Restoration73]

Two speakers, so
https://www.radiomuseum.org/r/regentone_a_3532a353.html

[Gabe001]

My 358 has a stamp on the chassis, see attached.

They're well built, look and sound lovely. Yours looks like it's in great condition

Gabriel

[Radio Tech]

Hi restoration73

Definitely not the 352/353 model, as the one I have has all octal base valves and the fact it has the AZ31 rectifier this made me think it was what I said. I will see, I am just about to start work on this set.

Ken

[Trifocaltrev]

Hi I think this earlier model is your one.

Regards
Trevor.https://www.radiomuseum.org/r/regentone_a353a_35.html

[Radio Tech]

Hi folks

Got the chassis out to start the work needed on this and just out of curiosity the only number I can find on the chassis is AF0911 I have a feeling this is a serial number. Thanks for the link Trevor but when I looked at the information, the valve bases are not octal they are of the 6f series, only v4 of the A353 model has the octal base. In both circuit diagrams the smoothing cap appears to a 16+16uF but as the A358 has a AZ31 the max capacitance for the reservoir is 60Uf so I am considering putting a 50+50uF in.

Ken

[Cobaltblue]

The radio in the Radiomuseum linked to by Trevor (Regentone 353) has the following valve line up (and two speakers):

ECH35 EF39 EBC33 6V6 AZ31 all Octals

It seems there are two versions of this set the one linked to by Restoration is the 353/2 so a later version.

Cheers

Mike T

[Radio Tech]

Thanks Mike

Yes it does seem to be that way, two totally different versions, when I downloaded the circuit from radiomuseum it just showed the B8G valve bases on the schematic, the one I have does have that valve line up and two speakers but I cannot seem to find the exact service manual for this one I have, both circuits show only one speaker.

Best wishes

Ken

[Radio Tech]

Hi Folks

After changing the caps, I applied power and got some sound out of the set, but after around two or three minutes the sound fades, I set tested the EF39 and EBC33 and they seem ok, I could not set test the ECH35 or 6V6 and haven't got those valves as spares so will have to check the voltages around each valve and see.

Ken

[cathoderay57]

Tired AZ31 rectifier? Jerry

[Radio Tech]

Hi Jerry

Yes I did wonder if the rectifier was of this condition but I also wondered about the ECH35 going down, the reason I say this is that I hooked a scope to the grid of the EF39 and after a while the signal into the grid just went, now whether this is due to the AZ31 starting to fail I am not completely sure.
I just wish I had a spare ECH35 and AZ31

Ken

[Gabe001]

Ken, you don't need anything fancy to diagnose a tired rectifier, just your multimeter. Generally, the greater the demand on the rectifier, the lower your HT will be if your rectifier is "tired". Try measuring HT with and without the 6v6

See here

https://www.vintage-radio.net/forum/...d.php?t=169873

[cathoderay57]

Check the HT feed to the ECH35 oscillator anode. If the anode voltage is low because a resistor has gone high that could also cause the symptom. Jerry

[Richardgr]

By coincedence came across this, this evening ...
From a 1950 Radio Times, Issue 1371

[Radio Tech]

Hi Jerry

Yes I will check the feed resistors on those anodes and Gabe001 yes will check voltage off rec with and without the 6V6 in.

All the usual caps have now been changed, I did check the HT on both sides of the smoothing cap and this seems ok.

Will press on with this,

Ken

[telstar]

Hi. I recognize this radio, a Regentone A353. mine has the I.O valves. These radios work very well indeed.
Good luck
Mike

[Radio Tech]

Well folks, this is quite a task so far, have checked AZ31 HT on both sides of smoothing cap and with the 6V6 out which reads 311V and 310V, with the 6V6 in 309 and 310V. The feed resistor of the ECH35 seems ok and if anything just reads a little lower than 47K.

Best wishes

Ken

[Gabe001]

Your rectifier looks ok. Play it through pickup and see if behaves in the same way. If it does, your problem is with the output stage.

[Radio Tech]

Hi folks

I injected a tone through the gram socket and the output stage appears ok so now it looks like the front end stage of the set failing, the odd thing is though the voltages around the ECH35 and EF39 seem ok according to the data I have.

Ken

[cathoderay57]

Hi Ken, hopefully the replacement ECH35 should sort things out. Maybe also worth checking the oscillator coupling capacitor(s) connected to triode anode and grid circuits of the ECH35. Usually these are silvered mica or ceramic types that rarely give trouble but faults are not unknown. Cheers, Jerry