Brenell Tape Machine Restoration

[Stevie342000]

I have just acquired a Brenell STB - 2, which is in need of some tender loving care - I have a separate request in parts section for items that are missing.

I resolved the initial issue of where to get the a full set of knobs from they are still available from RS Components - I finally found them.

Other than the knobs which are all missing, including the tape reel hold downs, the transit hold downs and the knob on the back panel not much else is missing.

Other than a damaged ECC83 the only other issue is the missing 1/4 track tape head (or at least I assume it is the 1/4 track that is missing, not checked the head track width. Oh yes and one other important thing that is missing some one has kindly removed the bias oscillator.

There was one surprise though as it has the built in valve amplifier which is in the back of the chassis. The control knobs for volume, bass and treble are concealed by the sliding panel on the back which has the mains in and on/off switch, plus two jacks which I assume allows you to use external speakers.

This was not a cheap machine to start with with a retail price in 1965 of £150 plus £25 extra for the stereo power amplifier.

I have the schematics and the instruction manual for the STB - 2 which needs to be read again and again it is complicated but simple really.

I just need help with the parts, I will go check known sources on eBay and I have contacted Geoff Kremer for what parts he may have, Colin Braddock as far as I know can not help, not contacted George West but he may be able to help with parts.

Any help much appreciated - I still have the STB - 1 to sort out. I now have all the semi-professional tape machines I need and enough work to see me through many dark winter nights.

Other than those small issues it is in good condition and the insides are clean the lurking dead spider is on the back panel air vent, the odd bit of dust and dirt inside but surprisingly clean.

Oops I forgot to ask I assume to get the electronics out I need to undo the 4 screws on the back panel and it all slides out, after having disconnected the tape transport leads of course, is that correct? I will go read the instructions to see what it says. I also assume that this applies to the STB - 1 as well?

[brenellic2000]

Unfortunately most STBs are 'well worn' - they tended to be hammered and then were discarded.

Yes, all those knobs are baffling at first - an owners manual is crucial - but once mastered are a joy to use. The built-in power amp is rarity - more photos please! My STB-2 has a Mullard transistorised set-up; some had monitor speakers.

Could you let me have the serial number please for my Brenell records... and is it an 8-1/4" or 10-1/2" model?

Spares are rarer than hen's teeth

Barry

[Stevie342000]

In reply the amp photos are 1 & 3, if I can figure out how to get the unit out of the box (I assume I take out the 4 screws on the back and that panel slides off and the whole metal cradle that holds the electronics slides out?)

At which point I can take some pictures of the undersides of the amplifier and other units. The one design point which could be an issue is the output transformers in that add on amplifier have the cores aligned on the same plane and not at 90 degree angle which could lead to hum implications and coupling between channels and effect channel separation but every design is a compromise between cost and acceptable results. Had they reorientated the output transformers cores on that amp it would have meant making the wooden case even larger in size than it is already compared to the STB - 1.

The knobs on the amplifier are Bakelite high quality and look like the knobs used on MK5 M.

Both the STB - 1 and the STB - 2 are the 8 1/4" models, so are less likely to be as hammered as the 10 1/2" versions.

Whoever bought this had a lot of money to spend, it was not cheap when it was bought, I suspect the valve amplifier units were only supplied for about 3 years from the introduction of the model in 1965.

Do you happen to know what the production ratios were for the models as the MK5, the MK5 M and the STB series as they are the same transport?

I know from your books that the machines were made in batches of 50 my assumption is they made a batch of 50 transports and then made X amount of electronics and mounted heads for each model type, is this a correct assumption?

I have more than one Brenell machine (all MK 5 variations (except special models) and one MK6 transport) and will pass on serial numbers as I come across them. But please see attached photos for the STB 1 and STB 2 which I took some moments ago and edited for your records.

In repairing either machine I assume all electrolytics should be changed, as well as the germanium rectumfriers in the DC heater power supply and all coupling capacitors. Plus spot checks on the high value resistors.

Open to suggestions?

[barrymagrec]

I would see no reason to change germanium rectifiers assuming they measure O.K.

[Stevie342000]

So what you're saying is as long as the DC heater voltage measures what the schematic says it should do then leave them in?

This of course would be done with the valves removed including the valve rectifier.

[barrymagrec]

I don't know the circuit but assuming no regulator all the DC heated valves will need to be in place to correctly load the circuit.

Germanium rectifiers mostly work correctly or not at all. They are also an unusual choice in this application unless they are being used for their low forward voltage drop.

I have done similar when the AC volts were in short supply, before the advent of Schottky diodes.

[brenellic2000]

Steve, removing the case screws/back panel to reveal the cradle is usually straight forward. As you note, the STB2 case is longer.

The primary difference mechanically is the superior optional hand-wound high torque Papst motors on the STB2. I suspect the batches of 50 Mk.5 decks included the odd STB... though it could equally be 50 STBs. As to production ratios there are too few STB survivors to make a sensible guestimate.

I see you don't include a Type 19 in your semi-pro machine collection; this is a quite different multi-function deck to the Mk.5/Mk.6 altogether. They did make a shorter knee-height (rather than arm-pit) 8-track version... !

Barry

[Stevie342000]

Oh now you've done it, a Type 19 is now on my list but I have never seen one come up for sale. I think the reason I have avoided that is that it is the machine if I remember correctly that is known as the Towering Inferno?

There are issues with this machine, the deck plate is not rigid enough and there will be azimuth and tracking issues. But yes it would look cool!!!!

Of course any Type 19 machines that do survive will be beat up but they are rather nice looking. I assume it used a master bias oscillator with buffers on each channel? My assumption is that it is beefed up version of the Brenell Tape link expanded to 8 Channels?

The other downer is that tape is not cheap once you get passed 1/4" and that in itself is not cheap these days, have you seen the price that the Rival companies metal spools of tape go for these days? I know it is Scotch or 3M (= Minnesota Mining & Manufacturing for those that do not know) 202 but really......

[Stevie342000]

Originally Posted by barrymagrec

I don't know the circuit but assuming no regulator all the DC heated valves will need to be in place to correctly load the circuit.

Germanium rectifiers mostly work correctly or not at all. They are also an unusual choice in this application unless they are being used for their low forward voltage drop.

I have done similar when the AC volts were in short supply, before the advent of Schottky diodes.

I am assuming that given that the machine was developed in the mid-1960s that silicon rectifier diodes where a few years in the future. If they are shot I assume 1N5402 would be OK but may need to insert low value high wattage resistor in series to bring down the DC volts.

I am aware that when using modern measuring equipment it does not load the system in the same way as the older equipment and the voltages you see may be slightly different to the ones on the circuit diagram. I have an Avo Model 8 not sure off my head which Mark it is but it is contemporary with most of the equipment I have.

[barrymagrec]

An Avo 8 should be more than good enough to measure valve heaters, meter loading is not an issue on such relatively low impedance circuits but you must have the expected complement of valve heaters.

Silicon diodes were well established in the very early sixties, Lucas were a pioneer in the field making low voltage high current type for motorcycle alternators. Leevers Rich used a Lucas bridge rectifier for the valve heaters in all their machines from circa 1962.

[Ted Kendall]

Originally Posted by Stevie342000

There are issues with this machine, the deck plate is not rigid enough and there will be azimuth and tracking issues. But yes it would look cool!!!!

Wot, no Cadey? Now that's a real Brenell-based bag of nails

[brenellic2000]

Hi Ted,

The early Type 19s deck was certainly 'wobbly' but its flexing was overcome by extensive bracing. It was available in every combination imaginable from ultra-slow to 30ips, 2 or 4 speeds, 1/4" to 24-track 2". I have 3 or 4 of them... and am still looking for a cassette replicator version.

The Cadey (Mk5 deck) ... yes, well... what can one say?! I can't find any nails in it but peek inside at the DIY-electronics and wiring at your peril!! The Mk.II with Cadey's own deck is apparently 'better'.

[Stevie342000]

There are not many Type 19s around I would think that were not in beat up condition, although they are designed for heavy use in a professional environment unlike the STB range.

I assume that once you get above 1/4" tape (as the Type 19 is designed for single track all the way up to 16 or 24 track)then the deck plate issues raise their ugly head?

I did not pay much for either of my STB machines the STB - 1 I got last spring and paid £75 for it. The STB - 2 I got last month and paid £55 for it, not vast sums but amounts I was willing to pay rather than the usual £300 to £800 price tag.

Whether the machines were somewhat of a bargain in comparison and they both need work (I assumed that this was the case before purchase) and I would not consider a higher price for the machines as they are likely to be just as beat up.

I have to say they are in remarkable condition but both have had modifications to them or are missing parts another reason I would not pay the higher price. Neither was sold with any photos of what was under the hood (tape deck plate), caveat emptor indeed.

Overall very happy the Type 19 would be a nice machine to round off the collection I know that would not be enough and I would then want to source the rarer then hen's teeth in a Tyrannosaurus Rex Model 7 and the Mini 8 the latter I would like but they are not cheap and they are going in need of serious maintenance after all these years.

[brenellic2000]

The 1" Cadey Mk.5 is unbraced and relied on an MFI MDF cabinet!

The Type 19 flexing was primarily down to the extra-wide deck plate but was easily overcome by a steel U-channel, for which there was ample room. Few sellers correctly identified these rare decks as a Type 19 on e-Bay, but yes l haven't seen any for some years; the last were ex MoD.

I know of only two Mk.7S having survived: mine (100% complete and mint) and a transport deck in Belgium: I have a couple of spare amps which seem to have been sold independently and more brochures than decks! There was a 4-channel prototype which disappeared from the works. The Mk.7S and Mini-8 are related.

All you need now is a Mk.6S and a 10-1/2" IC2000, a Charles Atlas course, a Mk.600.... or buy my collection!

[Ted Kendall]

Spaceward Studios had a 2" Brenell transport as their first 24 track machine. It didn't go well.

[barrymagrec]

A colleague went to the Brenell factory circa 1974 for a job interview. He was shown what may have been a prototype 1/4 inch deck perched on a stand and bowing by about a 1/4 inch in the centre, he wasn`t impressed.

[brenellic2000]

Ted, that was the later AH-B Mk.600 - its main problem was electrical rather than mechanical. Having bought Brenell for the Mini-8, AH&B lost interest in tape and the senior engineers moved to Soundcraft Magnetics to join Alex (ex-Brenell) and John Eustace who were developing a new studio deck from scratch...

Re Barrymagrec's comment, even the Mk.6 deck-plate can be made to bow with sufficient force and determination! I dare say a Tonka toy can be made to suffer..!

[Ted Kendall]

Whichever model it was, it was only the transport Spaceward used - they didn't have pots of money, but were stuffed with electronics graduates (the same company went into video effects shortly afterwards) so they made their own amplifiers. Legal action and all sorts...not pretty. To be fair, though, it wasn't as obvious at the time as it later became that transports for 2" tape are something different in kind, not degree - and even Leevers-Rich quarter inch decks flexed so much that the slow-speed operation in BBC Bush House, for which 150 machines had been expensively converted, was quickly abandoned.

[barrymagrec]

Leevers Rich decks did flex though the later machines had magnesium alloy deck plates and were better from that point of view.
My understanding of the Bush House 3 3/4ips failure was that it was largely due to the difficulty of satisfactory editing at that speed and the greater audible effect of a less than perfect edit.
I certainly agree that 2 inch tape is a different ball game, for one thing the low compliance of the tape means you need a much longer tape path or you have no chance of a stable transport.

[Stevie342000]

Those are the other machine brand that I have lusted over the years for, I had no idea Leevers-Rich machines were prone such problems as well.

I had thought they were much more rigidly made than the semi-professional Brenell.

I was aware of the wow or slow start up with the Leever-Rich machine and it was prone to snap or stretch tape. But my understanding is that the EMI BTR-2 was used for editing and the Leevers-Rich machines were used for programme and spot edits with a long leader?

But back to the Brenell I assume I should replace all the coupling capacitors and electrolytic capacitors? Are there are any known issues with components such as resistors which tend to go high or low?

And finally the suppressor capacitors are a known on my machines are the X or Y rated 250 V AC and what is the value?