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Old 25th Oct 2021, 8:16 am   #21
cambush
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Default Re: Bush Arena BH4000

Big Jim,

Many thanks for those PDFs. Is there any chance you could send the other half of the schematic, with the tone control circuit? The quality of yours is much better than the Radio Museum scans.

SJM,

No luck yet looking through the boxes. I think I'm resigned to re-using the ILP modules, which do work fine (even though I'll be using the +/- 30V supply rather than the rated 25V) at least until I find the time to make up new PCBs.
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Old 26th Oct 2021, 5:10 am   #22
Big jim
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Default Re: Bush Arena BH4000

Hi I've already sent the tone control
Circuit look in part 2
Jim
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Old 27th Oct 2021, 9:06 am   #23
cambush
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Default Re: Bush Arena BH4000

Sorry, thanks - got it! I've got the filter PCB out now and see that it is marked 6185C - the one in your manual is 6185B. I can see a couple of differences (e.g. mine has two slightly different DC supply voltages) but hopefully they'll be similar enough for me to make progress. Having pretty much dismantled the whole thing, I have to say that they must have been a nightmare to manufacture!
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Old 30th Oct 2021, 5:25 pm   #24
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Default Re: Bush Arena BH4000

Quick update - pleased to say that I found the fault with the filter board (a blown 100uF electrolytic). While I was there I replaced all of the 10uF caps too and a few 100uF caps too. Interestingly, they all measured about 50% capacitance over their marked value - possibly because of this... https://electronics.stackexchange.co...tance-with-age.

Pictures of fixed filter board (and nice new green lacquer) at https://photos.app.goo.gl/ufv1EtGxBB2mUBBP8

I'm completely amazed at how much work I must have done on this in a previous life - like the burned out tracks on the PSU PCB (see photos).
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Old 5th Nov 2021, 11:44 am   #25
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Default Re: Bush Arena BH4000

Hi - wondering if anyone could send me the PCB layout for the BH4000/T4000 power supply - mine has some burned-out tracks that I bodge-repaired in a previous life, but something doesn't seem right, and I'd love to check for sure.
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Old 7th Nov 2021, 9:44 am   #26
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Default Re: Bush Arena BH4000

hi hope this helps. jim
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File Type: pdf bush arena power supply pcb.pdf (2.55 MB, 17 views)
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Old 7th Nov 2021, 9:53 am   #27
Big jim
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Default Re: Bush Arena BH4000

part 2
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Old 7th Nov 2021, 5:34 pm   #28
cambush
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Default Re: Bush Arena BH4000

Jim, you're an absolute star! Now, what I don't understand is why the two centre taps (pins 3 and 7 at the transformer) which should both be grounded aren't joined on the PCB - indeed it seems to go out of it's way to avoid them joining. But on the schematic they are both connected to ground. Any ideas?
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Old 7th Nov 2021, 11:32 pm   #29
samjmann
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Default Re: Bush Arena BH4000

If you measure from ground to any of the fuses for the 31 and 23v supplies you should be able to measure a low reading. If not, check that there is continuity between the reservoir caps for the same rails and the transformers secondaries.

If the tracks were o/c there must have been heavy currents, I would have thought it would have blown the fuses.

I see what you mean about the track layout and the circuit diagram, the ground tracks appear separate. Maybe there is a jumper link?

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Old 8th Nov 2021, 11:10 am   #30
cambush
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Default Re: Bush Arena BH4000

I think the burned out tracks were a result of a younger version of myself replacing fuses with wrong values and suffering the inevitable consequences! I've now ordered a full set of new fuses.

I'm glad you agree on the PCB track layout, I can't understand it. I can only assume that originally the -30/0/+30 from the reservoir caps went straight to the power amp along with the shield from the pre-amp output coax, and that's where the two ground nets were joined. Unfortunately, neither the schematic nor the power amp PCB show explicitly the 0V rail from the reservoir caps connecting directly to the power amp, but I think that's how I'll reassemble it - perhaps it was done that way for some kind of earth loop reduction?
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Old 8th Nov 2021, 6:51 pm   #31
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Default Re: Bush Arena BH4000

I'm considering re-making the missing power amp PCBs, so in the (admittedly unlikely) event that someone else stumbles upon this thread looking for the PCB design, here's what I cleaned up from Big Jim's service manual scan... obviously it'll need scaling to actual size. The edges are a bit pixelated, but I'm hoping the etching process will smooth things out somewhat.
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Old 8th Nov 2021, 8:44 pm   #32
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Default Re: Bush Arena BH4000

I think you're spot on with the earth loop. Thinking about it what they were doing was star-point grounding. So heavy power output stage currents don't modulate low voltage supplies. This must be why the grounds are separate as you've pointed out.

I'll have to dig out my BH4000 from long term hibernation sfter reading this. All the electroytics must be near shot now. It did power on without smoke 10years back.

SJM.
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Old 9th Nov 2021, 9:22 am   #33
cambush
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Default Re: Bush Arena BH4000

SJM - if you do dig yours out, would you be kind enough to confirm the ground wiring as discussed? To be honest, although every electrolytic I've measured so far is 50% over value, apart from the one blown in the filter circuit the rest seem to be working OK. I did notice a date ink-stamped on the underside of the brushed aluminium case - 09 Aug 1974.
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Old 9th Nov 2021, 6:41 pm   #34
samjmann
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Default Re: Bush Arena BH4000

OK, it'll need a warm up as its in cold but dry storage. It's only been opened once for me to swop the tuner module back about 1980. It won't be till the weekend as I'm fully committed throughout the week. Mine was purchased about May 1975.

It's funny the way you can view something with a completely different attitude, often years later. The item hasn't changed but your experience has. I often think back and say, 'why on earth did I do that...'

Cheers, SJM
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Old 9th Nov 2021, 9:18 pm   #35
cambush
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Default Re: Bush Arena BH4000

Ha ha - yes, I know what you mean. I'm sure I didn't buy mine until probably 1975 or even 1976 - maybe it had been sitting in the shop for some time.

As if the electronics wasn't enough of a problem, I'm bamboozled by the arrangement of the string/spring/pulleys for the tuning indicator (see photo), so if you do get yours open I'd love to see how it should be done. I can't seem to get it in a configuration that allows the indicator to reach the full extent of the dial, but maybe it never did?
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Old 21st Nov 2021, 11:09 am   #36
cambush
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Default Re: Bush Arena BH4000

My repair and re-build is moving along - I have everything pretty much repaired and back together again (using the ILP amp modules for now). I need to mod the replacement tuning dial illumination bulbs - they're not tall enough to send sufficient light into the ends of the perspex. Also the main tuning knob is slipping (looks like I did a bodge repair on this in a previous life - needs a new rubber wheel making). All-in-all though I'm pretty pleased so far. The only switch that doesn't work is 'Silent' which is no big deal.

Could SJM or Big Jim possibly send me the parts of the user manual that talk about the various aerial connections? It sounds like the radio side is working but can't remember what sorts of aerials it likes and which connectors to use for which band.
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Old 21st Nov 2021, 11:46 am   #37
Edward Huggins
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Default Re: Bush Arena BH4000

The aerial waveband marking should be clearly shown. A simple "T" dipole for FM and a long single wire for AM will get you started.
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Old 26th Nov 2021, 8:47 pm   #38
cambush
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Default Re: Bush Arena BH4000

Thanks Edward. Just wanted to say thank a huge you to all those that helped me out - amazingly, given the degree to which I'd dismantled it, I've got it all repaired, cleaned up and back together in more-or-less working order. Just need to re-unite it with my Wharfedale Glendale 3XP speakers, Pioneer PL-112D turntable and Akai 4000DS tape deck and it'll be just like 1976 again!
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Old 27th Nov 2021, 9:44 pm   #39
samjmann
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Default Re: Bush Arena BH4000

I had my my BH connected to an old VHF TV aerial, it worked quite well on FM. As for AM as Edward points out a long wire worked well. The tuning dial was never well lit. It was quite dim in the middle.

I had much the same set-up as you back then, Akai4000DS, and a Pioneer PL-12D, B&O 3702 speakers. The speakers I was never that happy with as they were a bit bass light!

Great to read to read that you've got it going again, apologies once again for not getting the scan to you in time.

Cheers SJM.
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