Bush VHF61 'half resto' repair

[Katar83]

I was given a Bush VHF61 radio recently in a very poor condition and decided to give it a shot and make it usable again.

Radio came in one piece but inside looked like it came from a flood. There was no chance I would spend full day cleaning it so the entire chassis went into the dishwasher and it came out super clean. At this point, I've replaced 20+ capacitors(some exploded, other disintegrated in my hands while scraping dirt to find out what they were), replaced the wire going to the magic eye(as it barely had any insulation left), crossed my fingers and powered it up.

Radio came back to life so I've ordered a replacement tune knob(original broken), replacement front cloth material and cleaned up case and repainted golden surround so the exterior looks pretty much brand new(except for the dial glass which was too damaged to be saved)

Dishwasher treatment made most components visually the same but I think all is in order. VHF works absolutely amazing, sound is crystal clear but feels like signal could be stronger(magic eye maxes out at 3/4 on BBC2) and weirdly there is zero static between the station(maybe 5-6), I would think there should be some static in between?

I have not opened the VHF box yet and thought I would ask if there is anything in there potentially that might need to be replaced, I have also not replaced two silver mica flat capacitors as they are within 15% of original spec. They are 515pf and 450pf. Should I?

Also, it takes about 30 seconds for the radio to actually switch on, is this normal or is one of the valves is on its last legs?

I had trouble recognizing one of the capacitors too, I believe its a C58, connected to ground from the smaller transformer. The original one was a fairly small(maybe double the size of 0.04uf ones) Hunts cap, that disintegrated but was showing 0.5uF, when the schematics is showing 40uF in there, I have put a 40uF cap in there for now which is about 10 times larger but unsure if its correct one. Any ideas?

Except for lack of any static on VHF, the MW and LW reception is pretty much non existent. This is almost certainly down to broken ferrite rod in the internal antenna. I have glued it up now and will attempt to move the coils to whatever place they seem to be working best but was wondering if there is any way to improve reception that doesn't involve oscilloscopes and signal generators.

Any help would be appreciated

[G6Tanuki]

Are you using it with an external antenna or the built-in one? You really need a good antenna [ideally an outdoor one] to get the best out of these.

And with a good antenna, yes, they really do sound good! Probably one of the best-sounding British table-top radios of the era, you need something big like a Pye FenMan or one of the German Grundigs to get a better sound.

The lack of inter-station noise is disconcerting [my VHF81 is the same] but it's just a feature of the gain-distribution and limiter design.

[Nickthedentist]

These have a reputation of being excellent on VHF but mediocre on AM at the best of times.

[stevehertz]

Originally Posted by Nickthedentist

These have a reputation of being excellent on VHF but mediocre on AM at the best of times.

Many say the same about the larger VHF64, but I've also heard collectors say otherwise, that it's something of a myth. Personally I don't think you can beat the Grundig models of the same era.

[agardiner]

Putting it in a dishwasher! Well; that's one way of getting it clean.

[cathoderay57]

Agreed, but it's a wonder that the IF coils survived...... Jerry

[Katar83]

It was either dishwasher or a full day of cleaning it with a toothbrush and various chemicals, it was definitely dirtiest thing I've ever had on my work table and lets be honest, that sort of commitment is purely reserved for special equipment

I've put it back together now, experimented a bit with the ferrite rod and coils over it and found a happy spot for them where MW and LW kinda works so will fix them with some hot glue. At the same time I've also found a broken antenna wire so got that fixed too.

Radio on VHF sounds very good, I'm used to old Unitra radios which have constant transformer humming which this one doesn't at all. I was very much impressed with the sound quality. Only lack of static is still very confusing to me

Now just need to find a replacement dial glass and get the keys fitted correctly(they are an absolute pain to put back in it seems). BBC was blasting for the past 2 hours, will be on all day tomorrow too.

[Katar83]

Oh, in case anyone comes across this post and needs to know what will be needed to get this working...

How many Original Replacement Voltage Type
2x 0.01uf 10nF 350v
5x 0.01uf 10nF 400v
1x 5uf 5uF 50v
1x 0.005uf 4.7nF 500v
1x 0.047uf 47nF 500v
1x 47pf 350v
1x 7500pf 7.5nF 350v
1x 90pf 350v silver mica
1x 515pf 350v silver mica
1x 450pf 350v silver mica
5x 0.02uf 22nF 150v
4x 0.04uf 47nF 250v
1x 0.001uf 1nF 400v
1x 0.003uf 3.3nF 300ac

[joebog1]

I have cleaned engine parts in a dishwasher but NEVER anything electronic, especially with IFT's and power and speaker transformers. I must say though, that has come up an absolute treat. Looks brand new!!.

Good job, but I will wait and see how long the transformers last.

Joe

[stevehertz]

Originally Posted by joebog1

I have cleaned engine parts in a dishwasher but NEVER anything electronic, especially with IFT's and power and speaker transformers. I must say though, that has come up an absolute treat. Looks brand new!!.

Good job, but I will wait and see how long the transformers last.

Joe

I have friend who sprays dirty radio chassis with Astonish brand alloy wheel cleaner, hoses them down, then submerges them in a bowl of water. Left to drip dry then placed in the airing cupboard for a few days. Swears he's never had a problem with IF cans or anything.

[Mr 1936]

Hi

We used to clean new PCBs at work in an ultrasonic bath using dry-cleaning solvent type stuff called Arklone. Then someone decided it was bad for the Ozone layer and we switched to pure water with a little detergent. As long as everything was dried off thorougly it seemed to work. However, there were no wound components where moisture could lurk or wax coated windings which could absorb water. One type of component couldn't be cleaned, which was a polyester "swiss roll" type capacitor with unsealed ends which wicked it up between the layers and suffered from a marked change in capacitance (water has a dielectric constant of 80). You could never dry those out.

I'm not sure why you changed silver mica capacitors, these are normally very reliable though nothing is infallible. Did they absorb water from the cleaning process ?

I wouldn't worry about the lack of inter-station noise. This seems to be a characteristic of 1950's sets, partly because they don't have enough gain to limit on noise. They were primarily designed for use with an external antenna in the same way as a TV set, unless you were lucky enough to live in an area of high field strength in which case the internal "reduced size" one would do.

[Katar83]

Chassis was dried thoroughly in the oven at lowest setting, circa 50 degrees with open doors and then was at room temp for a few days so was definitely bone dry, I was more worried about previous damp and probably water it stayed in as it had what I would describe as layer of dried mud over chassis. Also the dial glass sticker simply wiped clean off with close to 0 pressure hence me looking for replacement.

I've not replaced silver mica capacitors in it, was wondering if I should replace them, they are currently within 15% from spec, e.g 450pf is showing ~500pf.

The lack of inter-station noise is just confusing to me, I've never had a radio without it so when I switch it on initially and switch from MW to VHF and hear absolutely nothing my first thought is: 'did I just break it?'

My only unanswered questions are about that capacitor in the speaker transformer circuit, still not sure what value it suppose to be, currently using 40uF Siemens cap in there from a Grundig TK5 tape recorder and the fact that it takes approx 30 seconds for the radio to turn on. No idea if this is correct or not

Oh and maybe if there is anything that I should 'lubricate' inside the chassis except for dial needle slider which I already did.

[Mr 1936]

Hi

Using the Bush component designations, there are three HT smoothing capacitors sharing the same can:

C58 40 uF -20/+50% i.e. 32 to 60 uF Reservoir Capacitor
C55 20 uF -20/+50% i.e. 16 to 30 uF First HT Smoother
C47 40 uF -20/+50% i.e. 32 to 60 uF Second HT smoother

Although the draughtsman has shown C58 joined to the line going to the output transformer, electrically it is a conventional HT reservoir capacitor on the cathode of the fullwave rectifier V8.

There is no problem in using individual 47 uF and 22 uF electrolytics to replace the "triple can", provided C58 is suitable for the ripple current it will be tasked with passing.

[Sideband]

Not sure what you mean by 'takes 30 seconds to turn on'. Switch on, the dial lights should come on straight away. If so the set is switching on normally. Valves will take at least 30 seconds to reach emitting temperature, sometimes much longer depending on what types they are so there will be a delay before you hear anything. This is normal. Only battery valves give near instant operation since they don't have a cathode to heat up.

The lack of interstation noise is normal for a valve set.

[Vectis68]

The value of the brown "Hunts" cap on the audio transformer is .003uF And that is C67 on the trader sheet.

Phil.

[Katar83]

Originally Posted by Vectis68

The value of the brown "Hunts" cap on the audio transformer is .003uF And that is C67 on the trader sheet.

Phil.

Yeah, I've found this one, plus the C57 BUT on mine there is another cap and resistor which I cant seem to find on schematics, I thought it might be C58 but that's waaaay to large compared to original hunts cap.

I've attached a pic of the transformer with two squares where the cap is attached.

Originally Posted by Mr 1936

Hi

Using the Bush component designations, there are three HT smoothing capacitors sharing the same can:

C58 40 uF -20/+50% i.e. 32 to 60 uF Reservoir Capacitor
C55 20 uF -20/+50% i.e. 16 to 30 uF First HT Smoother
C47 40 uF -20/+50% i.e. 32 to 60 uF Second HT smoother

Although the draughtsman has shown C58 joined to the line going to the output transformer, electrically it is a conventional HT reservoir capacitor on the cathode of the fullwave rectifier V8.

There is no problem in using individual 47 uF and 22 uF electrolytics to replace the "triple can", provided C58 is suitable for the ripple current it will be tasked with passing.

Ah that makes sense now so the C58 is actually part of the 3 cap can. I've removed the 40uF and put the 0.5uF cap(which was what the old disintegrated cap was showing, still not sure what it suppose to be.

I have also managed to source replacement dial here, while waiting for it, I've decided to add 'blue teeth' to the pick up/gram input, instead the old school plugs I've opted for adding RCA socket(I had one already!), there is place for it under original pick up, then just added BT through RCA 2 to 1 mono cable, works well and I can listen to my podcasts now too, very happy with it!
While in there I've found another hidden hunts cap, between gram input pins, was badly out of spec so replaced it too. Very happy with how it works now, just need to wait for replacement dial now.

Oh and replaced power cable plug with the correct coloured one now too

PS
@Sideband
Thanks for confirming this!

[ms660]

Originally Posted by Katar83

on mine there is another cap and resistor which I cant seem to find on schematics, I thought it might be C58 but that's waaaay to large compared to original hunts cap.

C59 & R32 in the -ve feedback line ?

Lawrence.

[Vectis68]

That will be C68, 0.1uF.

See attached pic.

[Katar83]

Originally Posted by Vectis68

That will be C68, 0.1uF.

See attached pic.

Amazing, many thanks! Its not even on the schematics I've got here, that only goes to 62!

[Mr 1936]

Hi

I think we are getting mixed up between the Bush component designations and the "Trader" ones (this happens rather often !). They are completely different, because Wireless & Electrical Trader (WET) always drew their own schematics.

Bush C59 is the same as Trader C68, a 0.1 uF in series with the negative feedback line which runs from the output transformer secondary back to the volume control.