Ferranti RP1041 with Collaro Studio deck

[Edward Huggins]

Originally Posted by Audio1950

Ok, for a start, you can ignore all the previous references to the cartridge we assumed you had. Yours is an Acos GP67, which is strictly mono only, and there is no stereo stylus that would fit it.

You are are right then. That's the problem with assumptions when information from an OP maybe limited or (unintentionally) inaccurate.
I suggested the Studio "O" type as Collaro very rarely supplied autochangers to manufacturers with other than their own type already pre-installed.

[Audio1950]

I agree with you, Edward. Until this post, I don't ever remember seeing a Collaro changer with this style of arm fitted with any cartridge other than their own "studio" range.

[Audioevangelist]

OK that's useful to know, thank you.

Is it worth/possible to buy a new stylus for the Acos GP67 and will I damage stereo records if I do? In an ideal world I'd like to keep the knob on the front because it look right. However, if it is going to sound significantly better with the BSR X5M conversion then I will seriously consider it.

Before I do anything (including plugging it in) I want to replace the three important capacitors (C5, C6 & C12) in the amp. I am more familiar with solid state amps and that using high grade capacitors can improve the sound quality significantly. Is the same true with valve amps?

Given the relatively low cost of many of the components (apart from high grade capacitors) is it worth replacing other components to be on the safe side and to avoid having to dismantle it all several times? I'm inclined to do the best job I possibly can so that I get the very best from what is a good machine.

[vidjoman]

I thought the same about Collaro decks always being fitted with their own types of cartridge.
However much water has flowed under the bridge since the decks were made and anybody could have changed the parts around, overarms, cartridges and even complete arms that perhaps we should not 'assume' anything until pictures are provided as this always seems to lead to confusion. Even given numbers shown on labels may be wrong if it's been 'modified'.

[paulsherwin]

There is no point in buying 'high grade capacitors' for this or (arguably) anything else. I know there is an element of the hifi world which enthuses about certain boutique capacitors sounding better, but there is no real evidence for this even with high grade reference equipment, and this is a relatively nondescript old record player (though much better than many). Just use standard commodity plastic film capacitors. The sound will be exactly the same.

[Edward Huggins]

Originally Posted by Audioevangelist

Is it worth/possible to buy a new stylus for the Acos GP67 and will I damage stereo records if I do? In an ideal world I'd like to keep the knob on the front because it look right. However, if it is going to sound significantly better with the BSR X5M conversion then I will seriously consider it.

As already advised by me and others, even with a new stylus fitted in the GP67, it will still damage your stereo records. It's OK with old Mono LPs.
Be aware though that's it's quite possible that the greater part of your collection will probably be stereo pressings.
A stereo-compatible Mono cartridge is likely to sound somewhat better than the GP67 because of it's improved tracking and HF extension - but most importantly it will not cause any damage. If you do fit one, you will need to reduce the tracking weight to 4-5 grammes.

No point in putting "Audio Grade" caps in this, you'll not hear any difference - just make sure they are the right voltage.

[Audio1950]

Originally Posted by Audioevangelist

Is it worth/possible to buy a new stylus for the Acos GP67 and will I damage stereo records if I do? In an ideal world I'd like to keep the knob on the front because it look right.

Yes, you can still but a stylus for the Acos cartridge, but it will wreck stereo records. As I said in post #18, this cartridge is strictly mono only. The stylus is available here:


http://www.musonic.co.uk/index.php?m...oducts_id=3267

[Audioevangelist]

A mono cartridge is therefore not going to be used.

From what's been said, the choice of stereo compatible cartridge is between the BSR X5M and ACOS GP91-3SC - do you agree?

I'm interested in the view that Audio Grade Caps are a waste of time. In high end Electrocompaniet pre and power amps I have experienced a big improvement in using them. The stereo soundstage after the change was quite magical and the bass was much tighter. However, I do appreciate the mono amp in the Ferranti is a very different thing and the subtleties may well be lost on it! Not knowing much about valve amps that's why I asked the question.

[paulsherwin]

You are perfectly entitled to your opinion about boutique capacitors, but you should be aware that the dominant view around these parts is highly skeptical. You can search the forum for several threads on such topics, including discussions of the importance of blind comparison, confirmation bias and the placebo effect.

Please stay on topic in this thread though. Any capacitors with the correct values and voltage ratings will work in this case, including expensive boutique ones if you like them.

[Audio1950]

Originally Posted by Audioevangelist

From what's been said, the choice of stereo compatible cartridge is between the BSR X5M and ACOS GP91-3SC - do you agree?

In principal, yes, except that the Acos GP 91 has been obsolete for years, so the X5M is your only choice.

[Edward Huggins]

Originally Posted by Audioevangelist

A mono cartridge is therefore not going to be used.

Not quite so!
You will still be using a Mono only cartridge, but it will of a stereo-compatible type. This means the sound will still be in Mono, but the cartridge (e.g. the still available BSR X5M) will have a stereo (and probably a 78) tip, have a far higher vertical compliance and will not cause any damage.
It seems to have taken several Posts to get this over, is all clear to you now?

[Audioevangelist]

Thank you, that's really useful.

On the subject of capacitors, I have a circuit diagram for the Ekco RP329 (the same amp I understand as my Ferranti RP1041). Reading previous threads about replacements for C5 & C6, am I correct that 0.01uF/350V DC (10nF/350V DC) are correct or would I be wise to use a higher DC voltage capacitor?

C12 seems to give issues periodically. 1800uF/1000V DC appears to be the replacement but someone has used 1.5nF/400V successfully. I'm a bit confused about what I should use and would really appreciate clarification.

C4 also seems to give occasional issue and is 0.4uF. I'd be most grateful for advice as to what I should buy to replace it, including the DC voltage.

Am I right in understanding that the remaining caps are unlikely to give issue?

Thanks for the help. It's much appreciated.

[paulsherwin]

These capacitor values are not critical. You can use any voltage rating which is the same as or higher than the originals.

Modern caps used preferred values, so the nearest easily available values to 0.04uF are 0.033uF and 0.047uF. Either should be OK as replacements, but it's standard practice to round up, to 0.047 in this case.

Any consumer grade waxed paper capacitor of this era is likely to be leaky. There are differing opinions as to whether they should all be changed. Some restorers retain the original caps where leakage is unlikely to cause problems in the circuit, but I normally change the lot.

[Audioevangelist]

Thanks Paul. I'm with you on that. I'd rather change the lot.

So the DC voltage is effectively a maximum (though slightly flexible maximum). A figure higher than original will work as well. I imagine going lower is not recommended?

[Station X]

As Paul has said, the rule is to replace non electrolytic capacitors with new caps having the same or higher voltage rating than the originals.

The same applies to electrolytic capacitors, but it's unwise to greatly exceed the original voltage rating.

See this thread for information regarding old and new CAPACITANCE values:-

https://www.vintage-radio.net/forum/...ad.php?t=88767

[paulsherwin]

It's sometimes possible to fit a lower rated cap than the original, but not worth the hassle. Sometimes manufacturers would use higher rated caps than necessary because they had them in stock, or sometimes the different failure modes of modern caps allow lower ratings.

Many restorers keep a stock of 400V or 630V caps and never go lower (in valve gear at least).

[Audioevangelist]

I collected the Farranti RP1041 this morning, slightly sooner than expected. The date stamped on the case beneath the record deck is Sept 1960, which I imagine is the build date.

I've taken some photos of it too. Over all it looks to be in good untouched condition, at least to my relatively untrained eye. Obvious faults are: -

1. Off/On/Rej switch on the Collaro Studio deck has been forced an ideally needs a replacement knob.

2. The Collaro deck needs a thorough clean and lubrication.

3. On/Off/Vol switch on amp clicks on but when turned off it clicks as expected followed by a second click, as if something takes a little longer to react.

I have not plugged it in and don't intend to until capacitors etc have been changed.

I'd be very grateful for comments from those of you who know these machines.

[Boater Sam]

Here we go again, blanket cap change. Will it ever work again?

[Techman]

I agree, Sam.

I always do a quick 'static' check, then power up with caution to see what 'gives and goes' and only then start thinking about what parts need replacing.

[julie_m]

The only capacitors that desperately need changing before you apply power are the DC blocking capacitors from the triode anodes to the pentode first grids of the ECL82s. (If faulty, these can wreak the kind of devastation with which it is really not worth taking any chances.) Then apply power via a lamp limiter.

Further capacitor changes should be made on a one-at-a-time basis, testing after each one. Otherwise, if you miswire something, it won't be immediately obvious what .....

Also check that all resistors are within tolerance, and change any that aren't.