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Old 30th Aug 2017, 5:48 pm   #1
Ancient Geek
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Default Regentone A155.

Hello all!

I'm just starting on a Regentone A155 purchased from a local auction. I've a good idea what to do, having studied these forums extensively, but I'll doubtless be picking your collective brains from time to time.

The Regentone is completely free of woodworm for the simple reason that any insect life would be destroyed by the thick layer of tobacco tar. It was also full of bird seed...
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Old 31st Aug 2017, 9:31 pm   #2
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Default Re: Hello from another newbie.

Hi Steve, Welcome to the forum, I hope you have an easy repair to the Regentone, if you need it the service sheet is available top right of this page £1.99. I would advise at least changing C60 (Trader sheet) before applying power after the usual checks.


Best wishes, John.
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Old 1st Sep 2017, 9:47 am   #3
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Hi John, thanks for the welcome. I've identified five waxies that need replacing (on order from RS, should arrive today). Apart from these, I expect the electrolytics will be past their prime, and the EM80 has lost its pip, possibly due to someone trying to change it without doing the requisite amount of dismantling. The chassis and panel mounting grommets have decayed into an unidentifiable substance that may be new to science, and the entire set is so permeated with tobacco residue that it probably deserves plain packaging and graphic health warnings...
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Old 1st Sep 2017, 12:19 pm   #4
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Default Re: Regentone A155.

The smoothing and reservoir caps on these are pretty good, I have never had to replace one, so I would try reforming and using the original unless they show any signs of having vented before.

These are good radios and well worth restoring.

Steve
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Old 1st Sep 2017, 4:45 pm   #5
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Default Re: Hello from another newbie.

Quote:
Originally Posted by Ancient Geek View Post
The chassis and panel mounting grommets have decayed into an unidentifiable substance that may be new to science.
That grommet goo (or something looking like a fruit pastille) is well-known amongst those who restore old sets.
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Old 1st Sep 2017, 6:43 pm   #6
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Default Re: Regentone A155.

This same chassis was used in a number of Regentone and RGD badged Radoigrams from 1955 and 1956. Many tend to pooh-pooh these Plessey made chassis, but these are as well made as any other mid-range unit of the period and sound just fine, especially in the "3D" models.
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Old 1st Sep 2017, 8:56 pm   #7
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Default Re: Regentone A155.

Hi EM80's are quite cheap, very much less than the older EM34's etc.
It should turn out to be a good restoration.

Ed
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Old 2nd Sep 2017, 9:27 am   #8
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Default Re: Regentone A155.

Thanks for the encouragement, folks. I'm a little nervous about trying to reform the smoothing caps, as I don't have a reformer or variac and my ancient HP bench psu only goes up to 50V. Any advice in this regard?

Steve
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Old 2nd Sep 2017, 2:11 pm   #9
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Default Re: Regentone A155.

A lamp limiter is easy to build to start up a set gently. In fact it is better than a Variac (other variable autotransformers are available) since the rectifier goes from no output to large output with a very low change of input voltage.

You could disconnect the smoothers from the rest of the set and feed them with a fat resistor (10k?) from the rectifier. This will limit the current and the voltage will rise gently.
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Old 3rd Sep 2017, 11:44 am   #10
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Default Re: Regentone A155.

Well, looks like it's going to be a good 'un. With a total leakage current through C59 C63 and C64 of a measly 10 microamps at 50V, I thought I'd give it a try with a lamp limiter.

With the limiter, LW sprang into life and all looked well. Without the limiter, MW and FM started working smoothing C59/63/64 remained cool as a cucumber after 15 minutes. Without limiter, and also with the EM80 and dial lamp, total quiescent consumption is 45 watts.

There's a fair bit of distortion, but I've only replaced C60 so far. Hum is very noticeable with volume set to max. The volume and tone pots are atrocious, as expected. There's also some noise on turning the FM tuning cap, plus there's some whistle between stations.

I've measured voltages on V5 and, oddly, they seem high:

Anode: Expected 260, actual 285
Screen grid: Expected 235, actual 270
Cathode: Expected 7.5, actual 7.9

The correct tap on the mains transformer is connected, and our mains voltage is around 236. All voltages were measured with a DVM, but since they were all at low impedance points I wouldn't expect much of a difference with an Avo.

Next step is to replace the other TCC waxies.
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Old 3rd Sep 2017, 1:21 pm   #11
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Default Re: Regentone A155.

The higher cathode voltage indicates that V5 is passing more current than expected. This should lead to lower anode and screen voltages, not higher ones.

Check R39, R40 and R41 (Trader Sheet).
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Old 3rd Sep 2017, 2:31 pm   #12
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Default Re: Regentone A155.

Thanks for this, Graham.

But conversely, if the HT were, for whatever reason, higher than usual, this would lead to higher screen voltage and cathode voltage, due to higher current, wouldn't it?

In any case, R39, R40 and R41 are all within tolerance. R39 = 44R (spec 39R), R40 = 1.65k (spec 1.5k) and R41 = 186R (spec 180R)

Screen current is 4.1 mA, trader sheet says 4.5
Cathode current is 42.5 mA, assuming C62 is not grossly leaking, which would make the anode current about 37.5 mA vs the trader sheet's 36.

Or am I talking complete nonsense?
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Old 3rd Sep 2017, 2:41 pm   #13
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Default Re: Regentone A155.

Going back a step, have you checked the voltages on V6 the rectifier?
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Old 3rd Sep 2017, 3:11 pm   #14
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Default Re: Regentone A155.

Hmm. 277V RMS each anode, cathode is 316V.
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Old 3rd Sep 2017, 3:33 pm   #15
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Default Re: Regentone A155.

Trader sheet says the voltages were derived from the manufactures information, usually mains supply voltage and mains selector tapping are given but not in this case, you could measure the heater voltage and use that as a figure for comparison in percentage terms.

Lawrence.
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Old 3rd Sep 2017, 4:03 pm   #16
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Default Re: Regentone A155.

I'm seeing 6.58 V RMS on the main heater winding, 'Y'. 'X' is higher as there isn't a dial lamp or EM80 to load it down at the moment. So, yes, it looks like everything's running about 5% high.

Last edited by Ancient Geek; 3rd Sep 2017 at 4:24 pm.
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Old 3rd Sep 2017, 4:06 pm   #17
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Default Re: Regentone A155.

From the manufacturers service data.

V6 anode 255V 46mA
cathode 280V 75mA

Readings with AVO model 8 230VAC input, vol control at min, AE shorted.
reservoir current = 85mA
power consumption = 220mA AC

If you need other voltages I will try to provide them.

Steve
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Old 5th Sep 2017, 5:56 pm   #18
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Default Re: Regentone A155.

Well I'm still a bit flummoxed by the high voltages I'm seeing. The screen grid voltages all seem there or thereabouts, but the anode voltages are all high, except for V2a which is about right, and the heater voltages seem high, as previously noted. I've used three different meters, which all agree. It all seems to be 10-15% high.

Having said this, the set seems to perform reasonably, although some alignment seems in orded. One oddity I did note is that I can receive a faint-ish BBC Radio Gloucestershire (1413 kHz) somewhere below Radio 4 LW. Would this be due to LO harmonics?
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Old 6th Sep 2017, 10:54 am   #19
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Default Re: Regentone A155.

A resistor in series with the primary of the transformer will drop the voltages. Since the HT is taken in pulses the effect on the HT will be greater than the heaters.
I do not know the tolerance of the heater voltages but 5% may be near enough. HT a bit high should not be a problem.
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Old 6th Sep 2017, 1:50 pm   #20
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Default Re: Regentone A155.

Thanks for this, Trevor. Bearing in mind other people's experiences with using DMMs to measure anode voltages in valve radios, I've managed to locate an Avo I can borrow, just to be sure that I'm not tilting at windmills. I agree that 5% on the heaters is probably OK.
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