AC 128/176

[reubensm]

That cart looks like the Shure M75ED (cant tell for sure as the picture is not very detailed). If it is then matching N75 styli from Shure or Jico could be a good match. I have a lot of experience with the Shure M75-6s, what a under-rated cart it really is, with its N75-6 stylus, it could produce some great sounds

 

[dr.partha]

Thanks a lot again...

 

[dr.partha]

I removed the stylus today and found it's a Classic 700 Cart. The cart sounds really nice for old LPs. Can you please advise me which stylus (for LPs) should I buy for this cart in place of Shure 78 stylus?
Regards

 

[reubensm]

I am not very familiar with the classic 700 cart but owners have told me that it is very good. I think All India Radio also used these cartridges. I am not sure about which stylus to use but given that the Shure N78 was working with it, perhaps other Shure Styli especially those compatible with the M75 series cartridges, will work. However, I look up to knowledgeable forum members to comment and suggest.

 

[dr.partha]

After much googling, what I have found today is- the attachment!!
Please have a look and advise me are they real Germanium transistors? Or they are silicons?

 

[dr.partha]

I've found them on Aliexpress.

 

[reubensm]

They look like genuine transistors but its hard to say whether they are germanium ones. Also you may want to keep an eye open as shipping from China to India seems to be a bit of a problem these days.

 

[quad]

One possibility is to look for a 60s or 70s transistor radio , perhaps on OLX, and
see if they have suitable germanium transistors (likely).

 

[reubensm]

AC127 or AC176 (n-p-n) is the transistor which is a little hard to find, a lot of the transistor radios of that era had transformer based output stages, using 2 x AC128 (older ones would have 2 x OC72) with an output transformer, like in the schematic snippet below.

More upmarket transistor radios (especially the ones that had FM bands, eg: Philips) and Radio-recorders (boom boxes) from the late 1960s and early 1970s used louder and better amplifiers and it is in these that you are likely to find these n-p-n germanium output transistors. Here is a schematic example:

 

[reubensm]

so Dr.Partha, did you order the AC176, AC128 pair from ebay? Any progress update?

 

[dr.partha]

so Dr.Partha, did you order the AC176, AC128 pair from ebay? Any progress update?

Yes. Sorry I couldn't reply as I was diagnosed as COVID positive and was seriously ill (a bad virus, no doubt). Now I'm fine.
I found AC 187/188 pair after much "scrap haunting" in old repair shops. I found 2 pairs. One of these pair has already been installed on my HMV fiesta with proper precautions.
Now the player has come to life again with much more loudness and clarity! I am happy and really want to show gratitude for your kind help.

 

[dr.partha]

so Dr.Partha, did you order the AC176, AC128 pair from ebay? Any progress update?

The pair coming from ebay is still on the way !

 

[dr.partha]

And I've kept one pair as if it is made of gold. Probably, I shall use it in some other record player.

 

[reubensm]

Yes. Sorry I couldn't reply as I was diagnosed as COVID positive and was seriously ill (a bad virus, no doubt). Now I'm fine.
I found AC 187/188 pair after much "scrap haunting" in old repair shops. I found 2 pairs. One of these pair has already been installed on my HMV fiesta with proper precautions.
Now the player has come to life again with much more loudness and clarity! I am happy and really want to show gratitude for your kind help.

Happy to note that you have fully recovered. I wonder when this pandemic will end. It is causing so much inconvenience for so many. Yes, these old germanium transistors are quite good for these small applications. As they were widely used in those times, finding replacements are not difficult but requires some looking around. However they are fast disappearing so good to keep a few as spare.

 

[dr.partha]

Exactly said. I'm thinking to search for another couple of pairs if I can.
Thanks.

 

[Douglas]

Hi. I have tried with ECG103A, 2SD72, AC127 NPN transistors in complementary with 2SB405, and BEL AC128 PNP transistors. Whereas PNP transistors are intact but all the above said NPN transistors found with collector to emitter leakage but no other faults. That leakage introduces some hum even when I keep the volume level zero. All the NPN s have been purchased from the overseas. To fix my vintage radio I have tried with all the originals but that leakage pissed me off. So I have decided to use LM 380 / 386 in the output stage and I also have TIP31A & TIP32A transistors for the complementary configuration. I may choose either the complimentary one or LM series based output amplifier. The radio functions with 6V DC. It has a full wave rectifier using DR25 germanium diodes akin to AC128 TO1 metal package.
Kindly drop your suggestions how to make the audio output stage successful.
Thanks