Sharp Transistor 10 BXS-330 radio help please

[jascha]

Hi everyone,
I have a vintage Sharp Transistor 10 BXS-330 that belonged to my dad and for many years this Radio was neglected as it didn’t work. I would like to get it back to work and I have some questions please.

Firstly this uses the following germanium transistors:
2SA80, 2SA82, 2SB74, 2SA14, 2SA12, 2SB75, 2SB156
I have not tested anything yet but the radio is totally dead. I suspect the output transistors have failed (2SB156). I would like to replace all 10 transistors with equivalent silicon ones. Anyone knows please what the modern equivalents are to the above mentioned transistors? I would also replace all electrolytics too.

Finally, there’s are very unusual socket that serves as ac in which is an in between a 3.5 mm and a 6.3 mm jack. Any ideas what size of plug this socket takes please?

Many thanks

[paulsherwin]

I would strongly advise against replacing all the transistors with silicon as this is unlikely to be straightforward. In fact I wouldn't even replace them with Ge equivalents unless they're actually faulty. Why do you think there are transistor problems? Japanese Ge transistors aren't known for faults.

It's much more likely that the failure to operate is down to switch contact problems or bad electrolytics. Time for some systematic fault finding.

[Station X]

Hello and welcome to the forums.

Please don't replace transistors or other components just because you think they might be faulty. That's a recipe for disaster.

Have you considered that the problem might just be dirty contacts on the earphone jack or AC adaptor jack? Check the simple things first.

If no joy you'll need to take voltage readings, start round the output transistors. Post the results here and someone will advise you.

[Station X]

Posts crossed, but we're singing from the same hymn sheet.

[jascha]

Hi, thanks for the advice. I shall of course check for faults before replacing stuff but I’ had bad experience with a Uher 4000 with bad transistors and therefore I’m presuming it’s them in this case. Electrolytics will be tested for high esr of course. I shall do the basic fault finding first such as faulty speaker, switch contacts, although I have already shot them with contact cleaner. I don’t want to replace anything that might throw the alignment out. I suspect a problem in the amplifier section however. It hasn’t been used for probably 30 years! No sign of life. Any news on the ac adapter jack please? Where can I find such a thing? I only tried to power it up using crocodile clips connected to the batter terminals feeding 6v dc.
Thanks for all your help so far

[Refugee]

I would go for that external AC adapter socket first.. Make connections where the wires go to the PCB. We all know how much trouble adapter sockets are like as they still can't get them reliable on modern laptops and phones.
The ear phone socket will have to be next.
You need a meter with a continuity beeper at least to test the basic electrics.

Do remember that it is a positive earth set and that all voltages are measured with one lead on the positive terminal of the battery.

[TrevorG3VLF]

I am a strong believer in getting the DC conditions correct first. Measure the voltage of the emitter, base and collector of all transistors. There should be about 0.2V between base and emitter. I would expect 10 to 20mA set consumption.

The AC adaptor is not AC, it is a 6V DC supply as you have used.

[camtechman]

JASCHA,

Any news on the ac adapter jack please? Where can I find such a thing?

The "JACK PLUG" that fits the DC socket (marked AC Adapter) is 4.0mm and on my Sharp BXG-370 I replaced the socket with the more common "Barrel & Pin" type of today as I never tracked down the correct plug.

It's not like the common 3.5mm & 6.3mm of today which are usually used for audio input or output, the socket on the Sharp is insulated and (as far as I can recall),1 side of the connectors is connected to the chassis.


Here's a pic of my model

[camtechman]

JASCHA,

To follow on, here's the link to my original thread, when I enquired about the very same Sharp 4.0mm plug problem 5 years ago and NOTE, it turned out to be 4.5 mm !!

https://www.vintage-radio.net/forum/...=sharp+BXG+370

[Beechcraft100]

Originally Posted by jascha

Firstly this uses the following germanium transistors:
2SA80, 2SA82, 2SB74, 2SA14, 2SA12, 2SB75, 2SB156
I have not tested anything yet but the radio is totally dead. I suspect the output transistors have failed (2SB156). I would like to replace all 10 transistors with equivalent silicon ones. Anyone knows please what the modern equivalents are to the above mentioned transistors? I would also replace all electrolytics too.

I agree like most if not faulty dont replace. A few tests would help however equivalent as follows

2SA80 and 2SA82
EQ is AF124 AF126 AF200 2SA218 2SA227

2SA12 and 2SA14
EQ is AF124 AF127 AF200 2SA201 2SA203

2SB74
EQ is AC125 AC126 AC151 2SB54 2SB56

2SB75
EQ is AC125 AC126 AC151 2SB54 2SB56

2SB156
EQ is AC128 AC153 AC188 2sb405 2SB475

They were germanium for a reason keep them that way

My 2 penneth over

Andy

[MotorBikeLes]

Interesting to note on the Circuit Diagram, it is SHARPE, not SHARP. When did that change. A bit like To Shiba becoming Toshiba, Lucky Goldstar becoming LG, and others.
Les.

[Graham G3ZVT]

And National Panasonic.

I don' think there is any significance in the "E" at the end of Sharp other than a typo. I think the circuit in the screenshot came from
http://www.kevinchant.com
A random dip into the the Sharp circuits held there brought up this one with SHARP and SHARPE on the same page.
http://www.kevinchant.com/uploads/7/...222_tr-223.pdf

[Herald1360]

Originally Posted by Beechcraft100

[

They were germanium for a reason keep them that way


Andy

Because suitable silicon either didn't exist or cost more at the time?

The reason to keep them that way is because it's a lot simpler than redesigning and modifying the set!

[Hybrid tellies]

Just like to back everyone up here. These are nice solid little radios with a good circuit.
If it is completely dead the first suspects will be the switch contacts of the on-off switch, and the switch contacts on the back of the dc input socket and headphone socket.
If these are ok some voltage checks will soon lead you to the fault.

[jascha]

Thank you all so much. These forums are wonderful and to know there’s so much support. It will be some days to go till I can have a look properly at the radio due to work however but will update as I go along. I haven’t taken it apart yet but wanted to post my questions straight away. I understand that GE transistors tend to be noisy hence my thoughts about replacing them? I also noted that one black cable attached to the internal aerial has come unsolderered from the circuit board and have no idea where it should go! That’s going to be a pain to trace! I doubt I can find an input dc jack that’s around 5mm in diameter? Any ideas or tips please?
I shall check the switch contacts again and do some basic testing. As long as the two ning section is all fine I should be able to get it going hopefully. Thanks for the equivalents Andy
Cheers

[paulsherwin]

Ge transistors are poorer performers than Si in most respects, but you can't simply swap them over without circuit changes. The radio will be fine with the original Ge types if they are working properly.

[jascha]

I just hope they will test ok as it will save a lot of hassle. The caps however must have by now dried up and no harm done to replace the dodgy ones. I look forward to get it back to work. It does need btw an antenna as the original one mostly vanished and all there is left is the metal housing of the original. Where can I find a suitable replacement for it please? Maplins? Cricklewood El?
Cheers

[paulsherwin]

It will almost certainly use a ferrite rod for MW so you only need a telescopic aerial for SW. You will need to measure the dimensions of the original and try to find something that matches - a forum member may be able to help. The telescopic rods used in Poundland TV aerials can be suitable in some cases.

[Station X]

Originally Posted by jascha

I also noted that one black cable attached to the internal aerial has come unsolderered from the circuit board and have no idea where it should go! That’s going to be a pain to trace!

As shown on the circuit diagram you posted, the "rod" antenna goes to the short wave antenna coil. It shouldn't be too difficult to trace. You may be able to see the remains of the wire on the PCB.

Originally Posted by jascha

The caps however must have by now dried up and no harm done to replace the dodgy ones.

Please leave the caps alone until you done some basic testing. Once the radio is working you can change them ONE AT A TIME.

[camtechman]

you only need a telescopic aerial for SW. The telescopic rods used in Poundland TV aerials can be suitable in some cases.

I doubt the type required will be available from Poundland.

The particular type of telescopic aerial for this radio has a threaded bolt at the bottom end which screws in to socket at the rear R/H of the radio. See marked up pics (yellow circle) and further pic of my radio with the aerial located.