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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 29th Jan 2018, 12:20 pm   #1
alpharadj67
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Default Newcomer - request for help with Alba 338 (Chassis RP5)

Hello everyone.

I am a complete novice in electronics and vintage record player restoration and would really appreciate some guidance on the following. I have acquired a vintage record player model - the Alba 338. From the really wonderful threads I have read on the forum I have been able to clean up and free the record deck which is a BSR UA15SS. The cartridge, which is a BSR X3M works well - but the amplifier keeps cutting out. Typically it will work for a few minutes (after having stood unused for a day or so) but suddenly cuts out. I do not think this is a cartridge problem as all sound including any low hiss/hum from the speaker suddenly disappears. I have checked all wire connections and nothing seems to have come adrift. I have a suspicion that it is probably one or more of the components on the amplifier. This model is and early transistorised machine and from appears in the 'Radio and TV Servicing' 1972/73 book but I suspect it is older - circa 1967? There is no evidence of any work having ever been carried out before on this - the amplifier has an appearance of having been untouched since leaving the factory. There was also a lot of dust within the casing. If anyone has any ideas as to how I can proceed to get this working I would be hugely grateful. I can solder fairly well and have grasped the basic idea that V=RI. Beyond that I am struggling to progress. I would really appreciate any help.

Many thanks
Rupert
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Old 29th Jan 2018, 12:32 pm   #2
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Default Re: Newcomer - request for help with Alba 338

I cannot find the circuit in the Service Data on this site so could you post the circuit and some photos of the amplifier etc.
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Old 29th Jan 2018, 12:33 pm   #3
Edward Huggins
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Default Re: Newcomer - request for help with Alba 338

It's possible that the volume potentiometer will need to be sprayed with a contact cleaner (Servisol) in the first intance so as to eliminate that.
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Old 29th Jan 2018, 3:48 pm   #4
Phil G4SPZ
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Default Re: Newcomer - request for help with Alba 338

The speaker itself is not beyond suspicion. Could you temporarily connect another speaker, or even a pair of headphones, as a check?
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Old 29th Jan 2018, 10:11 pm   #5
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Default Re: Newcomer - request for help with Alba 338

Quote:
Originally Posted by alpharadj67 View Post
... I can solder fairly well and have grasped the basic idea that V=RI...
I really like that - a good place to start
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Old 30th Jan 2018, 10:57 am   #6
Edward Huggins
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Default Re: Newcomer - request for help with Alba 338

I can't find this ALBA version. Is the model number correct? As always photos will help.
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Old 7th Feb 2018, 7:00 pm   #7
alpharadj67
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Default Re: Newcomer - request for help with Alba 338

Hello again and thank you all so much for your quick and helpful responses. My apologies for the delay in coming back. I had to leave off my restoration project for a while but now I hope to continue until it's finished.

Here are the pieces of action I have taken in line with the great suggestions made. Nuvistor - attached is the service data I took from 'Radio & TV Servicing' 1972/73. Also, some rather poor quality photos (afraid I don't have very good camera) which I took of the player and its amplifier.

Edward, I saw exactly the same model of record player for sale on-line recently where the seller had included the original purchase receipt in the sale. This showed it as being the 'Alba 338', so I'm only assuming I have the correct model no. In fact my machine doesn't have either a model or serial no. on it. I have sprayed the recommended contact cleaner into the volume potentiometer (also the separate bass and treble controls) but it made no difference - the amplifier will sometimes come to life for a minute or two but then all sound dies - not even a hiss.

The pilot light works but glows very dimly - like a torch with a flat battery.

Phil - I tested the speaker by taking a feed from the headphone jack of my CD/radio/cassette player and it worked very well over a few minutes. I suspect I'm at a point where I may have to start testing components - but I could be 'jumping the gun'. I have a cheap multitester and cheap capacitor tester and no knowledge other than following instructions and basic logic. If anyone can point the way further, I'd be indebted!

With thanks again to you all,

Rupert.
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Old 8th Feb 2018, 7:27 pm   #8
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Default Re: Newcomer - request for help with Alba 338

Try this test. Unscrew the brass heatsink for the germanium transistors from the central aluminium fin, do one at a time, leaving the transistor 'floating'. Then retry for a few minutes at low volume. Use it just long enough to see if the sound stays on.

In my experience, there will be a 'tin whisker' problem in the transistor(s) meaning the cases are no longer isolated. You should soon be able to tell which component is the culprit and can be replaced.

It may also be the driver transistor which is sometimes not heatsinked, but do the above first.
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Old 11th Feb 2018, 4:29 pm   #9
alpharadj67
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Default Re: Newcomer - request for help with Alba 338

Good afternoon Ben. Firstly may I thank you very much for your timely assistance. This has worked!!! I detached both the brass heatsinks from the aluminium fin and the amplifier has worked continuously well over long testing periods over the past two days without any problem at all! (I would add that to me the record player has a really pleasant warm bass tone, and a very high volume capacity). I am extremely grateful for your help.

On first detaching the heatsinks, the amplifier put out a low hum and for some reason the pilot lamp glowed very much more brightly, however, on turning off and then back on again, the amplifier came to life and has since worked well as it should, performing well, but with the pilot light barely glowing again. I’m aware that this is a diagnostic process and that the fault(s) will have to be put right. Having read the following threads I am not sure how the transistors are coded, and as I detached both heatsinks at the same time which one (if not both) is problematic. Also is the dim pilot light symptomatic of a component problem? Will try to find the codes of these transistors and also identify which is faulty. Many thanks again for your help, will report back. Best regards, Rupert.

http://www.vintage-radio.com/repair-...or-faults.html

https://www.vintage-radio.net/forum/...ad.php?t=76440
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Old 11th Feb 2018, 6:15 pm   #10
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Default Re: Newcomer - request for help with Alba 338

The output transistors are probably either AC187 & AC188 (NPN & PNP respectively) or AC127 (NPN) & 128(PNP), Other types have been used but the above were the most common. Either can suffer from the 'tin whisker' problem, which is why removing the cooling clips allows them to work normally, since the two metal cans are now isolated from each other. These should still be available, though a Google search might be needed to find stockists. I'd be inclined to replace both output transistors.
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Old 12th Feb 2018, 6:35 pm   #11
alpharadj67
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Default Re: Newcomer - request for help with Alba 338

Many thanks for your help on this. I have removed the heatsinks and found the following codes: the left hand transistor AC176 and the right hand AC128. I also removed the (floating) heatsink from the transistor marked TR3 on the service sheet and found this too is an AC128. Will aim to replace the output transistors as you suggest and will start an on-line search for a stockist now. Will report back in a few days' time - again many thanks for helping me. R.J.
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Old 27th Feb 2018, 10:34 pm   #12
alpharadj67
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Default Re: Newcomer - request for help with Alba 338

Hello again. I would like to give a progress update on this project and, if anyone can give further advice, I would be extremely grateful.

I bought two ‘new old stock’ AC128 transistors and one AC176 transistor and soldered them onto the amplifier (of course having removed the originals first). Prior to installing the newly acquired transistors I checked them all on a low-priced transistor tester which told me that they were all functional and gave the following readings:-

AC176 (TR4 output): hfe 41, Vf 150mV;
AC128 (TR3 output): hfe 53, Vf 130mV;
AC128 (TR2): hfe 87, Vf 130mV.

From doing some reading and research I’ve gained a basic knowledge of how Bipolar Junction Transistors work – but it is only a very basic understanding and I’m still not sure how to interpret the data. Anyway, this is something I will have to work hard on. The main issue is that the amplifier is not working properly at all now; the symptoms being as follows.

a) the loud steady hum which I mentioned in response to Ben’s comments earlier, which was an intermittent occurrence has returned, but this time it’s permanent. There is no hiss on the amplifier that I can hear and the volume of the hum is unaffected by rotating the volume or bass or treble controls. Also, the pilot lamp glows far more brightly than it previously did.

b) the two output transistors identified by Livewire get extremely hot after about a minute – almost too hot to touch (when I found this I shut off the amplifier and unplugged from mains immediately).

I am confident that I have connected the transistor leads correctly.

I’ve done some research on the forum and from this I am now wondering if there is a problem with the smoothing capacitor. I’m brave enough to have a go at changing it if this is the case, but will be guided by expert opinion. Any further advice or suggestions would be most gratefully received.

I’m afraid the delay in reporting back was due to having to wait for items to arrive through the post.

Regards from, R. J.
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Old 14th Jun 2018, 3:30 pm   #13
alpharadj67
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Default Re: Newcomer - request for help with Alba 338

Message to Moderators.

It's perfectly alright with myself to close this thread down - I've not worked on this model for a long time as it's a bit technically beyond me at the moment. I've opened a thread on a simpler single stage valve model which I hope is more in my league and have already had some superb guidance. Am indebted to the experts for the help and support given on this thread and may start a new one on this Alba model later down the line. With good wishes to all. R.J..
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Old 14th Jun 2018, 7:56 pm   #14
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Default Re: Newcomer - request for help with Alba 338 (Chassis RP5)

OK, if you want the thread reopening just report it (red triangle).
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