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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 14th Oct 2018, 5:51 am   #1
suebutcher
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Default Mystery PA with Sanken transistors

Which manufacturers tended to use Sanken transistors? I'm checking over a Japanese PA amp with Sanken 2SD257 output transistors, but it has no brand name. The model number is LBH-1021/01, it's 15 watt, and the front panel is black with a sort of Sansui/Realistic/Kenwood look to it.
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Old 14th Oct 2018, 7:11 am   #2
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Default Re: Mystery PA with Sanken transistors

I've had Pioneer and Marantz amps with Sanken Q's in, but that doesn't sound like yours. How about a pic?

Andy.
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Old 14th Oct 2018, 10:11 am   #3
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Default Re: Mystery PA with Sanken transistors

Here it is. Only the knob on the right is original, and a DIN mike socket has been added to the back. "LBH" makes me think of Leader, which had model numbers with similar prefixes, but I've only ever seen test gear from them.
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Old 14th Oct 2018, 12:22 pm   #4
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Default Re: Mystery PA with Sanken transistors

That looks similar to an old Tandy/Radioshack PA I used to have many moons ago.

So wondering if it may be one of those generic ones that got branded for any of a multitude of companies.
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Old 14th Oct 2018, 1:24 pm   #5
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Default Re: Mystery PA with Sanken transistors

Eagle is another possibility.
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Old 14th Oct 2018, 1:40 pm   #6
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Default Re: Mystery PA with Sanken transistors

It certainly has a 1990 cheap generic look to it. It's only 15W output so is certainly not a professional PA amp. Actually, it's hard to imagine what you would use such a limited amp for.
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Old 14th Oct 2018, 2:44 pm   #7
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Default Re: Mystery PA with Sanken transistors

15W into 3 or 4 horn loaded PA speakers is plenty for a local show or fete.

It does look to have a 70V line output.
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Old 14th Oct 2018, 3:22 pm   #8
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Default Re: Mystery PA with Sanken transistors

Ah, missed that. You're right in that case.
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Old 14th Oct 2018, 3:53 pm   #9
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Default Re: Mystery PA with Sanken transistors

LBH1021/01 (without the -, but that could have slipped in as Japanese manufacturers almost always write model numbers that way) is a valid Philips model number from their Electro Acoustics department. They didn't always make their own amps, especially the cheaper models. It doesn't look like it was ever touched by Philips, no type plate, etc. but I think the model number is too much of a coincidence.

I'd say it's not 1990's but 1970's.

Philips model numbers starting with LB are all professional audio products, the third letter and first number indicate the sub-category. Unfortunately the letters LBH1 didn't exist yet according to the 1967 model number decoding key that I have (it goes up to LBG1), but if I were to take a guess, I'd say the model was commissioned by a local Philips ELA department, for example that of the UK.

Either that, or it was made by a Japanese manufacturer that was great at trolling (I'm not sure whether Philips could claim copyright on the number format Lxxnnnn).

Could you maybe take a picture in which the specs on the back are a bit more zoomed in? I'd like to transcribe them in my Philips numbers database (with a tick in the box "more info wanted" so if anything turns up even a few years from now, I know to go back to this topic). Pictures of the inside, possibly from markings that could help determine the OEM and build date, would be nice as well.

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Old 14th Oct 2018, 4:28 pm   #10
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Default Re: Mystery PA with Sanken transistors

Date codes on components would help a lot.
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Old 14th Oct 2018, 8:50 pm   #11
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Default Re: Mystery PA with Sanken transistors

It certainly looks like the sort of thing that Eagle would have sold in the 1970's but I don't recognise the model number.
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Old 15th Oct 2018, 2:17 am   #12
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Default Re: Mystery PA with Sanken transistors

It's from 1979, there's just one date on a cable. Here's the interior, and a close-up of the model ID. The mixer board has printed resistors, and the three-transistor power amp is transformer coupled, the driver transformer being tucked under the board. The original knobs do look a bit Philips-ish, though I haven't been able to match them to anything else pictured on the Internet.
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Old 15th Oct 2018, 2:52 am   #13
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Default Re: Mystery PA with Sanken transistors

Thank you! For future reference: the amplifier board is marked PK-30A. The mixer board has printed on resistors. I think either JVC, Sharp or Pioneer used that technology but it may have been common for certain Japanese equipment of that era. 1979 seems a bit late but not too far out of range, but to confirm are there any date/batch codes on the Sanken transistors? Normally, semiconductors are a good indicator with a margin of roughly a year.

Also, aren't there any markings on the transformers? I think I see something on the side of one. Such markings might be useful in finding out in which brands they're also used.

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Old 15th Oct 2018, 6:28 am   #14
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Default Re: Mystery PA with Sanken transistors

The back panel looks like a TOA amplifier, they use the same blocks and the same anodised metal panel's and case construction. The designator looks TOA like too, but a search of their site reveals nowt, nor does a completed listing ebay search both in the UK and USA. A TOA amp would have "Made in Canada" not Japan.

Whatever it is, it looks well built using quality component's ( Rubycon caps), look at the size of the OPT, I bet it sounds well.

Andy.
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Old 15th Oct 2018, 8:17 am   #15
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Default Re: Mystery PA with Sanken transistors

The output transistors, Sanken 2SD257, have the code 9 N, the power transformer's marked UP 15H PT OE, the output transformer is marked UP 15 OPT OD with OE stamped on the top, and the mixer board says PRC HDK S6837 (and possibly more, there's components in the way.)

It can do 17 watts at 400Hz and above into 4 ohms before distortion, drops off to about 10 watts before distortion at 100Hz, and isn't usable below 50Hz, but that'd be fine for voice and background music. Apart from the power cord being cut, nothing was wrong with it. For all I know it may have been dumped because a couple of knobs were missing. Now to find someone who actually wants it!
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Old 15th Oct 2018, 10:53 am   #16
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Default Re: Mystery PA with Sanken transistors

The 240V voltage rating is unusual and implies it was made specifically for 240V countries such as the UK (and Australia?).
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Old 15th Oct 2018, 11:13 am   #17
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Default Re: Mystery PA with Sanken transistors

Quote:
Originally Posted by suebutcher View Post
It's from 1979, there's just one date on a cable.
Those dates just show at what point the cable type was approved by some certification body or other (is there a BS number nearby?), not the date of make. You could say that the unit can't be any older than this, but it may be considerably newer. It looks early to mid 80s to me.
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Old 15th Oct 2018, 11:22 am   #18
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Default Re: Mystery PA with Sanken transistors

Quote:
Originally Posted by suebutcher View Post

Now to find someone who actually wants it!

And isn't 12,000 miles away......
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Old 15th Oct 2018, 12:31 pm   #19
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Default Re: Mystery PA with Sanken transistors

No BS number, all the components including the wire are Japanese. Sumitomo put the year of manufacture on their cables for TEAC, for example.
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Old 15th Oct 2018, 2:31 pm   #20
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Default Re: Mystery PA with Sanken transistors

Quote:
Originally Posted by Diabolical Artificer View Post

Whatever it is, it looks well built using quality component's ( Rubycon caps), look at the size of the OPT, I bet it sounds well.

Andy.
The output transformer looks big because it has two secondary windings to cover 70V and 4 ohms.
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