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Old 21st May 2024, 12:10 pm   #1
LincolnG
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Default Restoration Vica 260 Radio

Hello,

I am restoring a Vica 260 Radio, from around 1955.

The radio seems to have had some work done on it in the past, to my eye, the capactors have been changed (they certainly aren't paper), however a long time ago. Perhaps somebody might comment.

Firstly though I am looking at the power supply. The AZ41 rectifier was broken, somebody had thought it a good idea to fit it back in the socket silicone cork. Luckily, the socket wasn't damaged.

An original 8 mfd cap. before the inductor (Speaker field, winding) reads very low, so will have to be changed. I've ordered some new ones.

The questions is, 2 other Electrolytic filter caps. have been added to the chassis, after the inductor, equalling about 30 mfd. Do I return the chassis to the original 8 mfd, inductor, 8 mfd or continue with it as modified?

Note: The schematic here does not show the values of both caps. I used another very similar schematic Radio Watt, Super 521 which has the same tubes and power supply, where all the values are listed.
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Old 21st May 2024, 12:36 pm   #2
Silicon
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Default Re: Restoration Vica 260 Radio

The capacitor C17 which is nearest the rectifier cathode is often called the Reservoir capacitor and should not be increased without consulting the datasheet for the rectifier.

I would install an 8 or 10uF capacitor.

The negative end of C17 should not be connected to the chassis because it would short circuit R13 which is used to generate a negative bias.

As a precaution, the metal can of C17 should also be insulated from the chassis.

The Smoothing capacitor C18? could be increased.

There seems to be a lot of the 'black tar' paper capacitors. They should be replaced.

Last edited by Silicon; 21st May 2024 at 12:38 pm. Reason: more info
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Old 21st May 2024, 12:37 pm   #3
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Default Re: Restoration Vica 260 Radio

I'd replace the electrolytics with values to match those on the circuit diagram. The two electrolytic capacitors are not in cans bolted to the chassis, so there should be no problems with C17 shorting out R13.

C10 and C11 need to be Class Y types as they're connected between mains and chassis.

Once you've got the power supply working check the output valve circuitry and work your way back towards the aerial socket.
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Old 21st May 2024, 12:55 pm   #4
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Default Re: Restoration Vica 260 Radio

The capacitor connected to the anode of the EL41 may experience high voltages due to its position in the circuit.
I would fit a capacitor rated at 1,000 Volts.

I would expect to see a capacitor between the junction of R9 and R10 and chassis.
It may have been left off the schematic in error.
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Old 24th May 2024, 8:51 pm   #5
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Default Re: Restoration Vica 260 Radio

Thank you for the helpful answers. I have ordered some modern electrolytics 8 mfd / 500v working and a new old AZ41. The Datasheet for the AZ41 does say that the PSU filter cap (C17), can be as large as 50 mfd. Although I am inclined that if C17 & C18 were originally 8 mfd, that it must have worked OK. It is agreed that C10 & C11 must be replaced, my similar schematic has a value of 0.01 mfd, and yes, class Y will be used.

The anode connected cap. EL41 to volume (feedback I presume) has the value 3k. Any idea, is that 0.3 mfd or 0.3nf

The question of a cap. between R9 & R10 to chassis is interesting, the Super 512 schematic has a single resistor of 0.25 R in this position (Anode EBC41), no cap. either: I wonder if R9&R10 were combined simply to get an odd value. And I don't think this set can be considered exactly over designed, more a cheap Spanish knockoff.

Following question 1. How do I best and most safely obtain the 125v (from 220) to opperate this. I would prefer an isolation transformer, (to put inside the case) but I can't find one anywhere. 120v Auto transformers are available in Spain quite cheaply, although very big and heavy.

https://www.leroymerlin.es/productos...1.html?src=clk

I have seen some videos of people using a pair of mains caps. in series across L & N as a potential divider, but I really don't like the idea of that. So, how do people normally do it.

Question 2. If I managed to get everything working, having replaced all the tubes, I presume both the RF and IF stages have to be adjusted. I certainly have no instructions on how to do that, will it actually receive anything ? Is anything being broadcast on SW & LW. Would I be better, just to get the audio stages working and then use an external source to get some sound out of it? Like a BT receiver or another form of tuner, for example.
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Old 25th May 2024, 12:31 pm   #6
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Default Re: Restoration Vica 260 Radio

I would not replace the valves unless I believed them to be faulty.
The radio will work with weak valves.

Capacitors, switches, resistors and the previous repairs are your main concern.
I assume that a capacitor marked '3K' is 3,000 pico Farads or 3nF.


The radio should work on a 120V autotransformer.
It may even work on 110V.
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Old 25th May 2024, 10:43 pm   #7
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Default Re: Restoration Vica 260 Radio

The Tubes have no markings (apart from the EL41) I tried, and failed to indentity that they were correct. They could have switched round, they could be totally wrong.
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Old 25th May 2024, 11:03 pm   #8
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Default Re: Restoration Vica 260 Radio

Ok, an autotransformer it is. How many watts do you think it needs to be? Once I have the rectifier and smoothing caps. my idea is to run it up with a 60w light bulb in series and go around with a meter to see if everything looks about right. Then starting with psu, then output, pre/detector working backwards to see what, if anything is working.

My biggest concern the that many of the values on the schematic are missing or unreadable.
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Old 26th May 2024, 10:56 am   #9
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Default Re: Restoration Vica 260 Radio

There is a website called r-type.org which has photographs of the valves you need to identify.

The power consumption will be approximately 50 watts.
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Old 26th May 2024, 11:40 am   #10
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Default Re: Restoration Vica 260 Radio

You certainly don't need a 500W transformer as shown in your link. 100W should be more than enough. Radios of this type normally use less than 60W.
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Old 27th May 2024, 12:58 pm   #11
LincolnG
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Default Re: Restoration Vica 260 Radio

Thank you
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Old 27th May 2024, 8:24 pm   #12
LincolnG
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Default Re: Restoration Vica 260 Radio

Quote:
Originally Posted by Silicon View Post
There is a website called r-type.org which has photographs of the valves you need to identify.

The power consumption will be approximately 50 watts.
The website tip was a massive help, from it, I was easily able to identify 2 of the tubes, the other, EBC41 (with 2 diodes), should be easily identifiable with my DUCROCQ tube tester (thanks Alain).
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Old 3rd Jun 2024, 11:10 am   #13
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Default Re: Restoration Vica 260 Radio

Got the replacement tubes and started on the power supply. Plugged it in with a 60w lamp in series and switched on. No bang!! It came to life, seems to be working, although it sounded horrible. Replaced all the capacitors, CBB22 (630v) mainly and a few in Y class, mains side and a few smaller values that I couldn’t get in CBB22. After, it sounded a lot better, although the speaker, has clearly had better days. So, removed the output transformer and cut the speaker down, to mount it, used purely as the choke. Bought a replacement Loudspeaker. I redesigned the line input to be a little less basic, straight into the grid EBC41 with a coupling capacitor. On line input it sounds great, I suppose it should, being class A. The radio works, quite a few radio stations at night (MW) although it’s very noisy, lots of crackling, hiss and buzzing. The SW doesn't pickup anything.

Question: Can anything be done to improve the noise on the radio?
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Old 3rd Jun 2024, 11:37 am   #14
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Default Re: Restoration Vica 260 Radio

MW and LW radios tend to pick up lots of noise from Switch Mode Power Supplies (SMPS) which are used in TVs, Computers, battery chargers, microwave ovens, DAB radios, WIFI routers, lightbulbs, etc.

Some of the interference comes through the air and some through the mains wiring.

Can you try the radio in a garden or balcony to get away from these noise sources?

The Shortwave band works best at night.
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Old 4th Jun 2024, 10:30 am   #15
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Default Re: Restoration Vica 260 Radio

Thanks for the responce. I'm not totally surprised. Also, nearly all the broadcasts seem to be coming long distance, kicking up the gain I suppose.

Getting a few cracks and clicks, no doubt some of the carbon resistors are bad. I've ordered some modern 1w metal film replacments.

Interestingly the radio has substantual deviations from the schematic, which is making things "fun".

Will the wirewound resistors be OK, or do I need to test them all as well?
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