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Old 4th Oct 2020, 12:49 pm   #1
chartz2
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Default Shearne Phase 2 Anniversary odd regulators

Hi,

I'm fixing a hen's teeth rare Anniversary (the one with a remote control, possibly from 2003 given its name).

The amp section is done, and works beautifully.

I have doubts as to how the preamp pre-regulators work.

Here's a schematic drawn after what's actually soldered on the PCB. Does it look right to you? The driver transistor was replaced (not by me) and the circuit looks odd - especially R2 and R5.
The negative rail is a mirror image, but of course with PNP transistors.

The amp is a failed repair by some incompetent tech from a well-known hi-fi shop. Ahem.

This is the regulator at top right of the picture below.

What do you think?

Cheers

Jacques

PS: not holding my breath, but if someone here has the complete schematics...
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Last edited by chartz2; 4th Oct 2020 at 1:02 pm.
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Old 4th Oct 2020, 1:36 pm   #2
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Default Re: Shearne Phase 2 Anniversary odd regulators

Looks like a reasonable regulator to me, I assume the second Vcc on the right is the output Vcc. R5 feeds the zener with the regulated voltage making it better, the R2 R1 combination "pot down" the output voltage to 12V +Vbe, I guess it gives 15V.

Upon second glance it is a rather clever design, not to hot on voltage regulation (won't matter in an amplifier much) but low noise because C1 decouples the output base. You won't get that in a 7815 (other regulators are available).
 
Old 4th Oct 2020, 1:41 pm   #3
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Default Re: Shearne Phase 2 Anniversary odd regulators

Looks pretty sensible to me. Q1 is the error amplifier, and the ratio of R1 and R2 together with the 12V zener (plus Q1's Vbe) set the output voltage. Q2 is an emitter follower to drive the output. R5 is there to make sure the zener gets current flowing through it. Because R5 comes from the output, the current through it and thus the zener is essentially constant, which is good for regulation.

The output from Q1 is aggressively decoupled by C1, which won't help the regulator's load transient response but will keep the noise down.

Chris
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Old 4th Oct 2020, 1:52 pm   #4
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Default Re: Shearne Phase 2 Anniversary odd regulators

Okay then!

Thank you both for very clear answers to my query.
I had never seen this before, hence the doubt.

Solved!
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Old 4th Oct 2020, 4:52 pm   #5
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Default Re: Shearne Phase 2 Anniversary odd regulators

It can start up because the base of Q1 rises more slowly than the output (Vcc the same name for two different rails will confuse people), scaled down by the potentiometer R2 and R1. While the emitter rises with the output voltage. This keeps Q1 turned off. R4 charges C1 and brings the output voltage up.

Eventually D1 starts conducting, stopping the emitter of Q1 rising, but the base keeps on rising, Q1 starts to turn on, and regulation begins.

There have been some regulator designs where once running they were OK, but they couldn't start reliably. It's worth checking.

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Old 4th Oct 2020, 5:41 pm   #6
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Default Re: Shearne Phase 2 Anniversary odd regulators

Okay, so I have to make sure that the cap is doing its job then, correct?
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Old 8th Oct 2020, 6:27 am   #7
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Default Re: Shearne Phase 2 Anniversary odd regulators

Happy to report that the amp works again! The above regulator supplies -/+ 18 V (?)

Does anyone know how I can find a suitable remote control?

The original one was lost and of course it isn’t in the Logitech database.

Thanks!
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Old 11th Oct 2020, 11:03 am   #8
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Default Re: Shearne Phase 2 Anniversary odd regulators

Anyone please?
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Old 11th Oct 2020, 9:23 pm   #9
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Default Re: Shearne Phase 2 Anniversary odd regulators

Is it just for the volume control and possibly Mute?
The trick is to find out what the remote control protocol used is. I suspect a sniff round the web is in order if there isn't a comprehensive service manual available.
Many UK manufacturers use the Philips RC5 system so its worth trying out a remote from say Arcam, rega, Marantz from its Philips days etc as I have a number of remotes here that work other peoples gear, which can be useful.

A.
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Old 11th Oct 2020, 10:00 pm   #10
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Default Re: Shearne Phase 2 Anniversary odd regulators

Thanks A. Yes, volume and mute.

I’ve already tried all the major British manufacturers as well as the Philips integrated amps of the era, to no avail.
I suspect an obscure Japanese rc protocol but all those I tried from the big ones, Sony et al don’t work.
The pic chip has a sticker but it doesn’t reveal anything.
http://vintage-audio-laser.fr/downlo....php?id=110391

Last edited by chartz2; 11th Oct 2020 at 10:06 pm.
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Old 12th Oct 2020, 4:51 pm   #11
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Default Re: Shearne Phase 2 Anniversary odd regulators

looks like you tried all the usual sources.
heres a daft idea,

If you can find someone with a working amp and remote control, they might be able to programme a "learning" universal remote.
I have such a beast in my toybox, bought it at aldi or lidl cant remember which for about a tenner, so they are out there for not much. basically you point the remote you need to clone at it and push the right buttons and hey presto.
Very long shot I know but possibly a solution.
There is another solution and possibly quite cheap. Depends on whether the owner is ok with a bit of circuit adaptation.
That is to disconnect the existing remote control circuitry, it looks like the standard Alps pot so its 2 wires to the motor, and I suppose the mute is simply a relay, again if you cant disconnect the relay power I think you could bypass it.
Then fit an aftermarket remote control board, they are out there.
HiFiCollective do a very nice one but its very pricy, works off the Philips RC5 protocol which is handy. I know it works having used it in a DIY project, handles volume and mute via a relay.
Since then I found out about the cheapo eBay controls from China. around a tenner for many of them, they all look the same and have as often as not an Alps RK168 pot on the board. You don't need that and I'd remove it and just use the control circuitry.
I've got one for a project and it came with a wee control so its all there. I have tested it sofar only with a battery and the bench PSU and its fine with about 9V up its supply terminals. Theres an onboard 5V regulator and a nasty little half wave diode rectifier which could be bypassed straight to the reg.
Worth thinking about if it could be neatly installed inside?
that way if you did get a genuine control or found out the protocol you'd be able to reinstate it easily.

Andy.
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Old 12th Oct 2020, 5:22 pm   #12
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Default Re: Shearne Phase 2 Anniversary odd regulators

Thanks Andy.

Yes, I had thought of that too, but then I'd have to find some way to light the remote and muting LEDs.

As for finding someone with the same amp... it seems to be as rare as hen's teeth.

A bottle in the sea.
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Old 16th Oct 2020, 3:33 pm   #13
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Default Re: Shearne Phase 2 Anniversary odd regulators

Hi,

The IR processor is a Zilog Z86E0412PSC. There was a sticker on it I just removed.
What does it tell you?

Thanks
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Old 19th Oct 2020, 6:47 pm   #14
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Default Re: Shearne Phase 2 Anniversary odd regulators

Sadly, that is a micro-controller, so the IR protocol is coded in the ROM. There is no sensible way of reverse-engineering the IR codes out of that.

dc
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Old 19th Oct 2020, 8:03 pm   #15
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Default Re: Shearne Phase 2 Anniversary odd regulators

Thanks Dave.
Probably the same Zilog in the original remote.
Oh well.
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Old 19th Oct 2020, 8:17 pm   #16
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Default Re: Shearne Phase 2 Anniversary odd regulators

Is there a part number on the IR sensor itself? It might be worth looking that up. Its properties might give a clue to the IR format. In particular, the carrier frequency is a good clue. From memory, the Philips RC5 and RC6 use 36kHz, many Japanese codes use 38.4kHz, B&O use 455kHz, and the old Plessey SL490 uses no carrier at all.

Chris
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Old 19th Oct 2020, 8:29 pm   #17
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Default Re: Shearne Phase 2 Anniversary odd regulators

Hi,
It definitely is a Vishay TSOP Chris.
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Old 20th Oct 2020, 4:13 pm   #18
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Default Re: Shearne Phase 2 Anniversary odd regulators

Well, there's nothing on the IR receiver. Just S04 and 60.
So, 60 kHz ? Mmm...
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