Pye Black Box BBH Mk2(?)

[Herald1360]

Picked up a nice Black Box yesterday- it's a (socially distancing) Repair Cafe job.

It's very nice to look at but I'm not sure it's original. The case is very (satin) Black and the BSR deck is a nice gloss black. Even the (Black and white) platter mat carries on the theme with a black artist(?) posed on a plinth.

It's reported to have a loud hum so hopefully it should be a fairly straightforward fix

More to follow as and when....

[Audio1950]

Definitely not original, sorry! The case was originally mahogany, the record deck was gold and beige, and the control knobs have been replaced. The volume and tone control knobs have also been replaced.

Barry

[Ed_Dinning]

Hi Chris, MK2 used PCL83 valves, MK1 EL series with a B8A base.
The MK1 was more robust with larger transformers, but still needed recapping or transformers would die.
The MK2 had smaller, easier killed transformers and was prone to HF (60KHz ) oscillations, usually noticed as a higher level of background noise ~ check with a scope

Looks like it has had the rattle can at it but it does look quite attractive

Ed

[Radio tirana]

Have to say I think the player looks great, before I had actually clapped eyes on one I thought a PYE Black Box was just that.
Hope the transformers are OK will follow the thread with interest
Kind regards RT

[Half a Mullard]

Looking at the deck I would guess it is the older version with the EL42 valves - agree with Ed (T shirt etc) the PCL83 version can be interesting this is the one which usually seems to be fitted with the Garrard Autoslim deck.

[nicam49]

Getting to the guts will be quite a challenge without disturbing that pretty good-looking paint job. Quite a transformation!

[Herald1360]

I've now "got at the guts". It was actually extremely easy- the transit screws were missing from the deck so this lifted straight out from the case. Several very handy little plugs and a couple of knobs later, the deck was completely free and the amplifier unscrewed and removed from the cabinet. The only slight inconvenience was the need to remove the mains plug to pull the mains lead out of the cabinet and move the amplifier from the dining room table to the workshop bench.

Consulting the service data and comparing the amplifier with it confirmed that the player is a BBH Mk. 2 with UL P-P EL42s rather than the triode connected EL42s of the Mk. 1. Not sure what model the PCL83 version would be, then. Mk. 3? Mk. 2a?

Evidence of being got at seems to be confined to the "upcycling" job and a bag with some of the original knobs taped the inside back wall of the case. No sign of any attention to the amplifier which looks clean and untouched, complete with all its little brown Hunts

More later......

[Herald1360]

I've had a preliminary look at the amplifier and established (thanks to the other BB thread running) that the main smoothing cap case is firmly connected to the chassis so that nice simple fix won't sort the hum problem.

I have to say that although it's a very neat looking and tidily wired little amplifier, it does rather illustrate what manufacturers could and did get away with in terms of bad practice in the layout of the PSU wiring. The main HT+ take off to the output transformer is direct from the rectifier cathode with several inches of spur wiring off to the reservoir capacitor +. The same approach is also taken with the resistor and capacitor decoupling the HT supply to the phase splitter and preamp stages- here the resistor connects directly from the OP TX primary CT tag to the various anode load resistors with another spur wire (about 6" long this time) running right across the chassis to the smoothing capacitor tag. It wouldn't have been any more costly to have "done it right".

Rant over!

[John10b]

I always take a few pictures before I start a service, they are handy to refer to, particularly if you have long gaps between doing the work.
John

[Edward Huggins]

Consulting the service data and comparing the amplifier with it confirmed that the player is a BBH Mk. 2 with UL P-P EL42s rather than the triode connected EL42s of the Mk. 1. Not sure what model the PCL83 version would be, then. Mk. 3? Mk. 2a?

More later......

We always called it the Mark 3. The OP transformers were different on the Mk1 and Mk2. As to the wiring, this was carried out by averagely trained assemblers and I agree some of these leads were too long. In my experience it was difficult to tell the finer points of the difference in sound as to the Triode or U/L EL42 versions. They were usually monitored, not on the speakers in the cabinet, but on a large open baffle with a 10" driver in the Lab. No transit screw were usually fitted. As to the use of EL42 (Car Radio valves) and PCL83 (TV valves) Pye had a huge stock of these ar the time. I would have prefered them to have used EL41s (nice as Triodes!) and ECL80s, and from 1956, the ECL82s. It was not to be.

[Herald1360]

Some useful progress.... after getting my head round the weird wiring of the output valve cathodes which took advantage of the ic pins also apparently connected to cathode

Evicted all the brown Hunts caps; only one of them measured leaky at 250V though and that was the one in the tone control circuit where it probably wouldn't matter. Replaced with assorted polyester types (even a couple of Mustards for the output grid couplers).

The output valves' common cathode resistor had drifted low, about 320R from 470R, this was replaced by a convenient but somewhat overkill 470R W22 which jumped out of the assorted wirewound stash.

One or two of the 20% higher value resistors were a bit over 20% high but they were left in place rather than bother with digging them out!

Initial turn on was undramatic but disappointing soundwise. A pin clean up, straighten and firm reinsertion of the ECC83 plus similar activity on one of the output valves brought things to life and another half hour was spent faffing around with dodgy 3.5mm jack plugs leads to extract audio from an old discman to see what it sounded like- pretty good if a bit quiet into the workshop speaker (a JVC bookshelf mini hifi thing probably expecting a bit more than 4W to blow your socks off!).

Here's a pic of the under chassis "after" view.

[Edward Huggins]

That looks very tidy. As to the ECC83, this could always be screened if required. At to your reference to 4 Watts, well in my experience and with good matching speaker/s, that can sound really loud. Your JVC speaker might well have been an 8 ohm unit and a poor match.

[Nickthedentist]

... and as Chris implies, it was probably bundled with an equally tiny CD/Receiver but sporting an output power of 50W per channel, and with plenty of "loudness compensation".

Connecting to the original, sensitive, Rola speakers (two x 3R in parallel) will no doubt make a big difference, especially with the lid of the player down.

[Techman]

If the player was originally in nice condition, then it's a shame, but assuming it was originally a tatty example, then I actually like it the way it's been 'modernised' and I think it would look good in any modern home - I like it!

I've got the PCL83 version of this player and I have to say that it's the loudest of ALL the record players that I own. I replace only the four critical Hunts paper caps and leave that harmless one in the tone control circuit.

I have to admit that I fitted a BSRX5M cartridge to the head and these are quite a 'loud' cartridge anyway. In fact I 'get away' with fitting these to single stage, single valve amplifiers, so long as not too much volume is expected when playing LPs.

[Herald1360]

I've now had it playing a record quite happily- it sounds a bit "boxy" but given its construction that's not too surprising.

However.... when turned off using its own switch, part of the tone control pot thus with the tone control fully anticlockwise it emits a most unfriendly squawk. I doubt it did this originally so I suspect something may be amiss with the peculiar feedback tone control arrangement- it doesn't seem to have much effect on the tone for starters.

Anyone come across this before or am I own my own here?

I'm going off Black Boxes already

[wd40addict]

I can confirm my MkII doesn't squawk. Tone control provides typical treble cut - you should notice a difference!

[Techman]

It's an odd one!

Some people have had a problem with them oscillating - I wonder whether the 'boxy' sound and then the 'squawk' at switch off is an indication that it's just on the point of breaking out into full scale oscillation and then does it just as it's switched off.

[Herald1360]

It's a pain, whatever it is.

It's reminiscent of a conditionally stable system which is fine until something, be it being driven into limiting or supply volts dropping or whatever, causes the gain to fall and off it takes!

I'll try looking very closely at the leading edges of a square wave for any interesting kinks.

I once had a biggish (1100A, 40V) dc psu with similar problems to tame at work but also a lot more sophisticated test gear to help with pinning it down.

[Edward Huggins]

I know what "Boxy" sounding means, but this whole unit was designed to sound anything but that way. I'm wondering whether you are getting a particular lower mid-range emphasis which might be linked to amplifier instability viz the "swawking/oscillations" - possibly a feedback loop issue?

[Herald1360]

Problem found- yes it was related to the odd tone control feedback circuit but nothing to do with the design. The replaced tone control capacitor was connected to the tag next to where it was supposed to go.