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-   -   Brenell STB-1 Restoration & Help Needed (https://www.vintage-radio.net/forum/showthread.php?t=135838)

Stevie342000 19th Apr 2017 12:21 pm

Brenell STB-1 Restoration & Help Needed
 
5 Attachment(s)
I acquired a Brenell STB-1 (unfortunately or fortunately depending on your perspective it was not the 10 1/2" spool version). It is in reasonable condition it is complete (including old round 2 pin plug).

Currently no idea if it works, upon opening it up there was a surprise (the head cover, plus 3 2uF 600v DC Aerovox capcitors (wedged in with newspaper - Sunday Times February 1968 it could have been 1988). Plus a couple of bags of bits all sealed up in envelopes in plastic bags - one bag was a Safeway bag which would figure with the date of the amplifier that I got with this lot in auction - the Brenell was listed at an auction house with a Technics SU-V3 which also has a 2 pin round plug on it.

Inside the other bag in the Brenell was the papst motor complete, with all fixings and screws. I had initially wondered why someone had put black masking tape around the capstan. All was revealed when I opened it up as the first thing I noticed was that it had a Ferrograph capstan motor in it (not sure what other mods have been made to the tape drive system).

The other modification apart from the capacitors which are not connected to the capstan motor as far as I can see that had no motor run capacitor - this might account for the tape on the capstan as it is probably slightly off speed or synchronizing to mains frequency.

Everything else is there including a mains light bulb with has a green wirewound resistor just sort of sitting on the mains cable - I assume the person did this as a temporary modification to replace the green resistor - which is there to drop the volts at 15 ips to stop tape snatch.

My queries are what should I do with it in regard to the mods? There is no way to tell if the papst motor has been repaired (I know they can go open circuit as can the Bogen Heads - there was a card in the motor pack for a business who dealt with motor repairs).

It all looks very neat and well made, with each valve section on its own little pcb - I can see what looks like black hunts capacitors in there and I know they need to go along with any electrolytics.

I could set up a light bulb limiter to put in circuit to test both the amplifier and the tape deck (although the light bulb in there may do the same thing - but I think that needs to go and to be replaced with the correct resistor? Plus I can take out the EZ80 in the PSU to test it section by section.

As for the motor is it possible to take another motor papst or AEI out of another Brenell Mk5 and put it in to replace the possibly dud papst and the Ferrrograph capstan motor.

I found the schematic for the Brenell STB-1 on line a week or so back when I bought the item. Oh right how much did I pay for the two items £70 plus costs total of £85.12 plus £9 more than that in total for P & P about £170 all told which is less than you would pay for the Brenell alone on eBay.

See attached photos and schematic I await your advice(s). The only other issues is that I missing the locking nut on the Bias Pot as it is loose - now I know what the piece of paper was for but wedged under another knob to the the left.

wd40addict 19th Apr 2017 1:12 pm

Re: Brenell STB-1 Restoration & Help Needed
 
Well the STBs are rare and worth fixing, but it's not worth proceeding with other work if the heads are O/C.

Motors etc can always be swapped from the much more common mono model and Hunts capacitors can always be replaced. I'm not sure if the capstan motor can be swapped from AEI to Papst or the other way round, but I'm sure Barry will know. Brenell deck finish went from gold to green (my favourite) to grey. I think AEI capstan was mainly the early gold ones.

If I were you I'd check the heads first (using say a 10k resistor in series with a DMM).

Stevie342000 19th Apr 2017 8:45 pm

Re: Brenell STB-1 Restoration & Help Needed
 
I would think that given the limited time the STB-1 was in production that it would be rarer than an STB-2 but you never know. The STB-2 was in production for at least 5 years from 1965 but in that time it got hellishly expensive and as sales were decreasing in the UK high fidelity industry in general and in reel to reel tape recorders especially with the encroachment of Far Eastern products. Plus the lack of advertising or reviews of Brenell equipment and other manufacturers in the UK.

Oh yes I agree totally with checking the heads to see if they are O/C. I have a similar Mk5 with a Brenell Tape link in my favourite too the green/blue colour, gold comes next for me and the grey just looks like it needs a good wash but is probably the harder wearing surface of the them all after the gold.

As most of the Mark 5 and come to mention it the Mark 6 to a large degree are based on the one design essentially they are just cosmetic variations, they would have had to have made changes to production using the press to make any real changes to the cut-outs and cost as well as ease of production by having one unified tape deck was the order for the day.

The electronics changed more over time. I have a Mk6 as well, which needs heads, head covers are there but no heads or electronics but I have a solid state version of the Brenell tape link essentially the same or similar to the 1970 wireless world publication.

They used the same heads for the solid state and the valve tape link plus I have seen that Servicesound have fitted some Brenells with Ferrograph heads (alleged to sound better too). I have some spare series 6 and series 7 Ferrograph heads as well as some stereo 1/4 track heads from Ampex probably 600 series or the like.

Yes I have a Ferrograph Series 7 as well as a Vortexion CBL6H (which needs recapping) and a Vortexion CBL5 which as far as I know has the low ht problem, so it does not stay engaged when put in to any function as it does not lock (a recent acquisition as well, I think it was like £100 and was local/ delivered the next day too after purchase).

Other machines include a Truvox MkIII I think it is, an Ampex 400 with early 350 electronics (mil-spec version circa February 1953), an Ampex 351 and every other variation of the Brenell Mk5 including a nice green/blue 10 1/2 " spool version. I have a Jason stereo Tape Link as well, plus a couple of Kellar KDB 1 (or 2 I think it is) dolby units with alignment tape and a set of instructions.

I have a staggered stereo Mk5 as well, as an Odd Brenell Mk5 (gold I think) which has mini-flux stereo heads. Something of a Brenell nut, just a STB-2 and 10 1/2" spool versions to go to complete the set. Would kill (not literally) for a Mk7 and a Ferrograph Logic 7. But I think I have enough tape projects to do as it stands.

Yes the Series 2 Mk 5 moved from AEI motors to papst for the capstan then I think it went all papst after that. I would imagine that you could swap the motors around Barry or some one else would know for sure.

I additionally have a full set (in colour - its a copy but a high quality one) of the instructions for a Brenell STB-2 - it is very high class for its time and much more comprehensive than the old gestetner copies for the earlier Mk5 series. Brenell probably produced the same for the STB-1 as they are very similar machines. I have a copy (somewhere in paper plus electronic copy) for the Brenell Valve Tape link. Plus most of the Vortexon schematics, amplifiers, mixers, tape decks and so plus Ferrograph of course.

The main difference between the STB-1 and STB-2 is an extra ECC83 (or 2) and the switchable gain in the feedback chain, the Valve Tape link is a derivative of the STB-1 circuit from what I can see.

Anyhow I digress as per usual, any help in what steps I should take to bring this STB-1 back in to play would be appreciated.

Stevie342000 19th Apr 2017 8:58 pm

Re: Brenell STB-1 Restoration & Help Needed
 
5 Attachment(s)
Here's a copy of the tape link circuit for those who wish to compare it to the STB-1.

It's digital origami as I scanned it from original documents years ago and used Photo shop to chop each picture so it was easier to see all the details. There are other parts to the schematic manual, I may have the instructions as well.

Ted Kendall 19th Apr 2017 10:08 pm

Re: Brenell STB-1 Restoration & Help Needed
 
Somebody's had a go at this, have they not? I'd be inclined to disrobe another of your decks and arrange them side by side so that you can see what's been changed and what hasn't. The light bulb mod may be for excess take-up torque on small reels at high speed - the Studer C37 did something similar, to good effect, so that's one thing I'd not chuck out without seeing if it works. Lord alone knows what the sticky tape is doing round the capstan, unless the Ferro stepped pulley is the wrong size - after that crude transplant, a little extra vulgar engineering would scarcely notice :-)

Stevie342000 20th Apr 2017 12:49 am

Re: Brenell STB-1 Restoration & Help Needed
 
Thanks Ted I will take it one step at a time but no impending hurry as the item has to be packed up soon as I will be moving a couple of doors down whilst my flat is being refurbished.

Just thought I would get in there and ask the questions to see where this all leads me with a bit of knowledge gained beforehand and during.

As far as I can tell the Ferrograph motor is fitted with the Brenell large capstan, the small 1/2" capstan is missing. I suspect the motor is not synchronising to the mains correctly either, as there is no motor run capacitor. But I suspect the motor may be self synchronising and it may not be necessary.

The electronics should not be hard to fault find along with replacing what I do suspect are Hunts capacitors, are there any resistors in this that may need to be looked at?

As for testing the transport, that should not be difficult, if I take out the rectifier in the amp unit, assuming the rectifier bridge in the heaters is not going to cause any issues either but would indicate if there was power to the amp unit.

I suspect Barry will have plenty to add when he gets around to seeing this but I may be wrong.

I have his books as well, I can highly recommend them to all who do not have copies, pretty sure that some have been updated and are currently on eBay.

Oh yes I think I might trade nearly all my machines, along with body parts for a Studer C37, I did have a Studer B62 with BBC mods out of BBC Leeds, sold it years back big mistake. Surprisingly compact in the metal case it was in too but a bit of hefty lift. The EMI TR90 went back to the person I bought it off but the only other machine would be an EMI TR52 C or D depends which was the 15 ips version. I have an EMI RE321 which I going to part with shortly.

The Brenells are well worth the time and the effort to get them all up and running, I have several transports which I could use for donor parts.

brenellic2000 20th Apr 2017 1:53 pm

Re: Brenell STB-1 Restoration & Help Needed
 
Hmmm.. thankfully I am not an audio-engineer so won't comment on the (so-called) mods yours has suffered! Whereas Brenell knew what they were doing, as time has shown, neither Papst nor Bogen did!

The STB-1 was short lived, but the AEI spool motors on the STB-1 are very reliable; the STB2 had Papst spool motors and on many the more professional/powerful Papst capstan motor which carried on to the Mk.6... however these still go o/c. It is entirely possible to re-engineer the deck plate to take AEI motors, but I suspect the task is too mammoth for most to stomach, so most will canabalise a decent deck... alas.

Likewise most heads can be fitted with simple engineering skills; one of my STB-2/10-1/2" has a Uher head. Here again Brenell's own heads rarely fail. The moral of this story is stick to an all-AEI Gold Mk.5 and fit stacked stereo heads... or the truly stunning Mk.7S - which is truly stunning and I know of one other (incomplete) example other than mine.

STB-1 vs STB-2? The STB-1 was half-heartedly aimed at the (home) studio market whereas the STB-2 was seriously aimed at the professional market and was far better specified; some had internal playback amps... but remember, they are mind bogglingly complex to use though very satisfying when working well. Most STB-2s were well used before retiring, so few survive in tact.

A decent Mk.610 stereo or a Type 19 is a worthy alternative... or indeed a Ferrograph Logic 7... or Revox A77!

Barry

Stevie342000 20th Apr 2017 4:05 pm

Re: Brenell STB-1 Restoration & Help Needed
 
Thanks Barry I have several Brenells some with AEI motors, some with a mix of AEI plus Papst for the capstan and some with all Papst motors.

I have Brenell MK610 that needs heads and electronics but is other wise complete, I suspect that the AEI and Papst motors will fit the same top plate no matter what model, given that a Ferrograph motor has been fixed to mine.

Will have to trace the circuit out and check out what the modifications are and get back here but given that I move in June that is not going to happen before then.

I have another Mk5 S2 or 3 not sure but it is the green version and that has been put in a home made unit no electronics with stereo heads and it fails to move tape when I put it into play position. I assume this is an indication of an open papst spool motor? It rewinds/fast forwards tape fine just does not play, it also has Bogen heads and no idea if they work.

The Mk5 that I have with the tape link if memory serves the erase head is fine, but there may be issues with one or other of the channels on playback again Bogen heads, that is also a green version.

The Tape link worked fine that last time I used it, never fired up the Jason tape link, its a very nice unit all black front fascia with copper banding yep real copper, funnily enough I think it pre-dates the Brenell Tape link by a few years it crops up in the old magazines. It was part of a range available in kit form as well.

I have plenty of spare tape deck units to use for spare parts and plenty of spare tape heads.

To be fair the STB-1 might have been a halfway house but it was streets ahead of the competition, functionality and sound terms but pricey. It came as no surprise that the paper used to wedge those capacitors in was a Sunday Times, the paper fits the income bracket of the person who would have been able to afford this machine or the STB-2. The Vortxion CBL machines were not cheap either but equally good machines.

brenellic2000 21st Apr 2017 2:12 pm

Re: Brenell STB-1 Restoration & Help Needed
 
Occassionally, Papst capstan motors can appear 'dead' on start-up, but if you let them warm up, and manually spin the capstan, they can often be coaxed into life... until the next time! I don't know when the Bogen/Papst failure issue first came to light - I suspect when resuscitating long disused decks shoved into dark, damp garden sheds - but the Brenell 'service manuals' (typed sheets) make no mention of such problems. It is however a cautious case of "use 'em, or lose 'em"... and I've lost a few decks over the years! Ho hum.

One day someone may be brave enough to offer a Papst rewire service... but I'm not holding my breath!

Stevie342000 22nd Apr 2017 12:16 am

Re: Brenell STB-1 Restoration & Help Needed
 
Thanks Barry that was a question I was going to ask as well. Would it be possible to have the Papst motors rewound?

Would it be expensive? Any Ideas or suggestion as to who could do it?

I suspect the use it or lose it counts for the Bogen heads as well? Although that may have more to do with the ingress of moisture as well as not being used.

The Issue with the Bogen heads and the Papst motors probably arose shortly after Brenell went out of business.

It may be worth me dropping AHB an email to see what they can suggest with the motors and the heads. Will add it to my never ending to do list.

brenellic2000 22nd Apr 2017 10:58 am

Re: Brenell STB-1 Restoration & Help Needed
 
Today's AH-B have no knowledge of Brenell tape-recorders. Papst no longer have any knowledge of their motors - likewise Bogen. But new tape recorder heads can still be made to very costly order. Talk to Terry Summers at Summertone. Realistically it is not commercially viable to make new heads or rewind Papst motors due to their complex internal wiring.

The last Phi-Magnetronic/Marriott based heads were made in 2010 and were an ideal alternative to Bogens .. not sure if Nortronics are still available - ask Geoff at SoundServices. It is alas now increasingly a case of breaking good decks for spares... something which I would hate to see happen.

Stevie342000 22nd Apr 2017 7:15 pm

Re: Brenell STB-1 Restoration & Help Needed
 
Thanks Barry I emailed Bogen some years back I got specifications on the tape heads used in Brenells, this was before your books came out, I probably still have it somewhere.

AHB is not a UK company anymore I think it is part of the Harmon Group, which may account for that (it is common practice to dump companies paperwork when you take them over, often just to wind up the concern and get hands on patents - EMI did it all the time, think Connosseur which was still a going concern when taken over). I sent then a letter way back in the 1980s when I got my first Brenell Mk5 S2 (all gold). I think I got a reply from Frank Underhill (I can not remember his name, I still have it somewhere) or someone that use to work for them he was out in Dorset way.

I have an old spec sheet from Phi-Magnetronics as I think he suggested to write to them.

I wondered if anyone knew of anyone who could rewind the Papst Motors ? But assume it would be expensive. I am surprised that Papst did not retain some information after all they are a German company like Bogen and would have thought that they kept an archive. It may have been at the time that it was stored somewhere but has not been scanned is available electronically. It is the way of things these days (even I am moving towards paperless (as much as possible)), I mean even th BBC does not have records any more it is all on digital storage. It is a cheaper form of archiving and takes up a lot less physical space.

I will add asking questions to Papst, Phi-Magnetronics and Bogen to my list to see if I can elicit any more information.

brenellic2000 23rd Apr 2017 10:49 am

Re: Brenell STB-1 Restoration & Help Needed
 
When AHB moved to Penryn they directed Brenell enquiries (especially Mini-8) to Frank, by then retired to his garden shed. A couple of AHB engineers at Brighton did try to resurrect the Syncon M24 and Model 600 but nothing much came of it.

Phi Magnetronics have closed. Your only real hope is Nortronics USA and possibly Photovox in Italy... you'll need a mortgage! Or make your own like many did in the 1950s!

Stevie342000 23rd Apr 2017 1:13 pm

Re: Brenell STB-1 Restoration & Help Needed
 
Thanks Barry, I was not sure oh the Phi-Magnetronics front if it was still around or not.

Yes I am aware of the Nortronics heads and there is a source of them in the US, as Joe Dundovic sold off what I seem to recall was his company to another guy whose name escapes me right now.

It seems that there are not that many quality machines (unless the heads are better than the plastic build or budget electronics inside) you can butcher to get 1/2 track stereo heads off, the choice is limited but not for 1/4.

What interests me is that the same heads where used with solid state and valves from Bogen by Brenell. That is not usually possible without some component changes to use a high or a low impedance head into a high or low impedance input.

Even the Nortronics heads will not be that cheap but they will be less expensive than getting them made new.

As for making them, that could be possible but I do not have access to the laminations or know where to get them from?

Plus I would need to make up a several jigs (which need to be very accurately made) and I am pretty sure that there are articles in Wireless World or some other magazine on how to make them. Plus there would be some maths involved as well, it is not as simple as it first looks.

I have never taken a Brenell (or some other manufacturers) head to pieces but I wonder if there is some way to take two mono heads and to flip one over so it forms the lower track and then to bring it all back together.

I will need to scour your tape manufacturers books to look for other suitable donor machines using Mini-flux, Marriot and other such heads for experimentation. But simplest option is Ferrograph Stereo heads any other cheaper and more plentiful makes for donors?

The buy a machine option as donor is no longer the cheapest option either have you seen the prices of some of the machines these days, Ferrographs were once very cheap, as were Brenells but not any more.

Ted Kendall 23rd Apr 2017 2:08 pm

Re: Brenell STB-1 Restoration & Help Needed
 
JRF Magnetics have the remaining Nortronics stock.

In my view, making your own heads is a mug's game - the principles are simple enough, but the devil is in decades of detail. Apart from anything else, they were generally made in two halves for ease of winding the coils and then assembled. The alignment of the halves and the production of a stable gap of the right dimensions between them is non-trivial. Repair is generally stymied by the fact that most of them are potted...

Half track stereo heads are scarcer because the format wasn't as popular as quarter track, tape economy being uppermost in the minds of most buyers at the time. The unloved Chilton machnes used Bogens, as did Truvox. Woelke (Miniflux) are worth seeking out - they aren't known to suffer the o/c problem.

Stevie342000 23rd Apr 2017 4:23 pm

Re: Brenell STB-1 Restoration & Help Needed
 
Thanks Ted I have a Brenell which was originally fitted with Miniflux (stereo heads - gold plate top if I remember - which is in line with adverts I have seen for the heads circa early 1960s) heads never new that they were Woelke.

Did Woelke not make the heads for the Revox G36 and Studer machines?

Yes agreed the 1/2 track stereo format was used more in the professional sphere than the domestic and of course tape was expensive as were tape machines compared to income and it gave you more running time for the tape used.

Plus 1/4 track stereo was a natural progression from 1/2 track mono, in that you flipped the tape.

Yes of Course it was JRF, I had forgotten who it was, will contact them as well.

Stevie342000 23rd Apr 2017 5:26 pm

Re: Brenell STB-1 Restoration & Help Needed
 
One for Barry, are the AEI and Papst motors directly interchangeable on the capstan side of things or the rewind motors for that matter (without having to re-tap holes or cut new ones)?

I assume they all use a standard distance and fixing holes. As far as I can tell the cutting, pressing of the top plate was done on the same machine from the start of the Mk 5 production run to its end with Mk5M in or around 1970 (its listed in the Hi Fi News year book in 1972, as was the Mk 5 S3, STB-2 ST200, ST400, MK6M plus variations including 10 1/2" spool where appropriate (the only difference being that I assume that the cut-outs for the spooling motor was done on a different press or machine for the standard 8 1/4" version and the NAB standard).

Their press may have been modified or the process modified to meet the Daphne Oram request for a 10 1/2" spool version - if she needed it then why not offer it as an option - assuming that they were not already working on it but the staggered head version she bought was a double slung MK5 rec/rep Amp with 10 1/2" spools. Never seen a gold 10 1/2" version come up for sale.

Oh right Prices:

Under Tape Recorders:
MK5 M S3 £116.45 plus PT £29.14
MK5 S3 £93.40 plus £23.38 PT with meter £99.49 PT £24.90
ST200 £116.00 PT £29.00
ST400 £116.00 PT £29.00
MK6M £124.00 PT £31.00

Under Tape Decks:
MK5 S3 £45.00 PT £11.29 (without heads)
MK5 S3 £49.95 PT £12.50

MK510 S3 £59.10 PT £14.79 (without heads)
MK510 S3 POA
MK6 From £47.85 PT £11.98 (without heads)
MK610 Full details and POA

Under Tape Units:
STB2 8 1/4" spool version £165.00 PT £41.29
STB2 10 1/2" spool version £187.00 PT £46.80
STB2 Monitor Amplifier £30 PT £7.51 (it has a separate listing and what looks like full specifications)

MK6 Stereo Unit £152.65 PT £38.20

Under Tape Amplifiers and Mixer Units:
MK5 S3 Record/Playback Amplifier £33.50 PT £8.38
MK5 S3 Record/Playback Amplifier (meter version) £37.65 PT £9.42
Mixer Unit £3.90
Hi Fi Tape Unit (Tape Link - solid state version) £73.00 PT £18.27

vidjoman 23rd Apr 2017 8:27 pm

Re: Brenell STB-1 Restoration & Help Needed
 
Way back in 60's I had a 5M which took 10.5 inch spools which had the extra grey top cover plate rather than just the sturdy deck plate. It had 2 AEI spool motors and a Papst capstan motor. Next I had an Stb2 with 10.5 inch spools that had 3 Papst motors. I also bought a 'spare' 10.5 inch gold deck with half track and quarter track Bogen playback heads for copying duties. Built my own transistor amps for that. Still have the gold deck somewhere in the depths of the storeroom.

brenellic2000 24th Apr 2017 10:31 am

Re: Brenell STB-1 Restoration & Help Needed
 
No, AEI and Papst motors are not 'directly interchangable', but with a bit of engineering skill, 'any' motor (or head) can likely be fitted... if you enjoy a challenge!

Yes, the Mk.4 to Mk.6 are essentially the same deck, but modified as they progressed - there are 3 variations to the 'gold' Mk.5. The Mk.7 and Mini-8 are similar developments, while the new multi-format Type 19 is unique.

The unmasked 'gold' deck plate (grey on the Mk.2) was usually for standard models with 10-1/2" models first offered in blue-grey metallic, but Brenell also offered the attractive blue-grey to customer choice. The hammered enamel helped mask spot welds on the deck plate - before going upmarket by settling on the aluminium deck-mask first in dove-grey enamel, then leatherette. These of course required removable of knobs to gain access, prompting the hinged STB-1 studio deck for the Mk.5 Series 3 and Mk.6. (The ST200 and IC2000 are a real pain to service).

As Ted says, making a head in two halves is a doddle - matching them up in perfect alignment is the problem!!! Yet, most of the early pioneers made their own heads - indeed, coil winders were a standard product in most High Street Radio Component shops. The more modern and advanced mankind gets, the less skilled we become in basic engineering and common sense!

As regards Miniflux/Woelke, the UK importers cunningly registered 'Miniflux' as their trade name when Woelke changed distributors... causing them, much to their chagrin, to adopt 'Woelke'. The Miniflux stacked-stereo first appeared on the 3-Star stereo and were briefly offered as an alternative to Brenell's own staggered-stereo set-up, which Daphne Oram used - these stereo MK.5s are big and very rare now... as is the 3-Star stereo.

Barry

Ted Kendall 24th Apr 2017 4:51 pm

Re: Brenell STB-1 Restoration & Help Needed
 
Dad had a staggered stereo which had been modified with two stacked R/P heads, with Brenell labels on - this so that the previous owner could monitor off-tape in mono or record in stereo without this facility. I played around with this machine n years ago and found it OK apart from the lack of synchronisation between the oscillators of the two amplifiers, which caused spurious tones to be recorded. Never got around to fixing that - a condensor linking the two oscillators would probably have sorted it out - and the machine has long since gone the way of all flesh.


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