Hello all? I have a bit of a problem and need some advice.
I resently was given an Amplifier that my late brother in law built. It is an EA Playmaster 136, can anyone tell me how to find a circuit diagram for it.
I can be contacted by email if that helps: auzzie2307@live.com.au
I am an electrician also so I know my way around a circuit and electronics also.
Thanks in anticipation.
I resently was given an Amplifier that my late brother in law built. It is an EA Playmaster 136, can anyone tell me how to find a circuit diagram for it.
I can be contacted by email if that helps: auzzie2307@live.com.au
I am an electrician also so I know my way around a circuit and electronics also.
Thanks in anticipation.
There's nothing like a schematic for the unknown that is unknown, if you know what I mean.
Likely, the 136, designed perhaps as an early effort by the current Silicon Chip Editor, is well known to him and there's a schematic and construction article available there. It goes back to the early 1970's so you have a few pleasant hours ahead swapping out caps before sending the semis also to oblivion.
As I recall, It was Electronics Australia's first and very popular budget kit amplifier design marketed in one box. Sound wise? Well, I did say early seventies and silicon there somewhere.
Likely, the 136, designed perhaps as an early effort by the current Silicon Chip Editor, is well known to him and there's a schematic and construction article available there. It goes back to the early 1970's so you have a few pleasant hours ahead swapping out caps before sending the semis also to oblivion.
As I recall, It was Electronics Australia's first and very popular budget kit amplifier design marketed in one box. Sound wise? Well, I did say early seventies and silicon there somewhere.
I recall "Playmaster" was a brand for kit amps sold by some Australian electronics magazine. I remember seeing some schematics online but can't remember where. There is a site named something like ozvalveamps.com, which is about vintage australian guitar amps. (I don't know if the site exists anymore, though). Quite contrary to the name it also included some stuff about SS guitar amps, so might be worth checking that out. It could be where I a saw those Playmaster schematics.
Thanks Teemuk, you're right. The site was operated by Roly Roper for some years but closed and now is back at this new domain: Classic ANZ Valve Guitar Amplifiers As the name says, it is 99% Australian and particularly DIY guitar amp designs by the EA magazine referred to earlier. There are references, (incorrect) to numbers 134 and 136 as possible solid state guitar amplifiers but these are just that, no detail.
Looking for an AY9171......Old thread, but...
All,
I have a Playmaster 136 with a broken AY 9171 transistor (the PNP part of the complementary output pair). I have a sentimental (ha) attachment to this old amp I built in 1973 and use in the shack but I can't get a replacement transistor. The only site listing it available (Nucleus) unfortunately tells me it is an error on their site. Can anyone help with one or a suggested supply? Happy to buy and cover postage. There is no apparent equivalent in a TO66 case, closely matched as it is to its NPN mate, the AY 8171 which perversely is still available.
cheers
AntonOfOz
BTW fault finding in this direct coupled amp was a b$%^&. The AY9171 has a shorted b-e junction.
All,
I have a Playmaster 136 with a broken AY 9171 transistor (the PNP part of the complementary output pair). I have a sentimental (ha) attachment to this old amp I built in 1973 and use in the shack but I can't get a replacement transistor. The only site listing it available (Nucleus) unfortunately tells me it is an error on their site. Can anyone help with one or a suggested supply? Happy to buy and cover postage. There is no apparent equivalent in a TO66 case, closely matched as it is to its NPN mate, the AY 8171 which perversely is still available.
cheers
AntonOfOz
BTW fault finding in this direct coupled amp was a b$%^&. The AY9171 has a shorted b-e junction.
Not sure where in Aust' you live but the big metropolitan libraries and the older Uni libraries will have old "Electronics Australia" in their shelves. May have to speak to a librarian but a place like RMIT in Melbourne is pretty accessible. I am in Qld now but I found Monash(Hargrave Engineering Lib)/RMIT/and Melb State Lib very helpful. You don't have to be a student and for the cost of a photocopying card you can get a lot of info'
But it will help if you know the year the 136 was published!
From Anton's comment sounds like it was pre-1973.
You might try "bumping" this thread this evening and see if people can be more specific.
Good luck, Jonathan
But it will help if you know the year the 136 was published!
From Anton's comment sounds like it was pre-1973.
You might try "bumping" this thread this evening and see if people can be more specific.
Good luck, Jonathan
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There is a thread here in diyaudio that might be worth following up it is called "PLAYMASTER 40/40 schematic needed" and the second post (#2) look promising because although it is the later 40/40 refered to this guy looks like he has all of the EA's
The thread is dated 31st August 2007. that might help.
For what its worth I just Googled Playmaster 136 and got some interesting sites.
The thread is dated 31st August 2007. that might help.
For what its worth I just Googled Playmaster 136 and got some interesting sites.
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Hi Anton
Here is an older thread that answers your questions but doesn't give you the antiques.
http://www.diyaudio.com/forums/solid-state/56192-fairchild-find-print.html
So you aren't the first to come up against TO66 power transistor problems. You'll see that no data sheets are availaabke for them but if you really want to know, perhaps Leo Simpson at Silicon Chip will assist, After all, it was his baby, AFAIK;
The TOP-66 plastic power types were developed to replace them wayback-even then. These will fit into the same holes if you trim off the collector lead and attach with the appropriate mounting bolt. I assume you can identify the connections of both original and replacement types. Don't forget to insulate with a new mica and grease, perhaps the old bush is OK.
What you need is a complementary pair (don't iust swap the bad one) that meets the AY9171/8171 pair spec. 35W output is max. rating. I believe the 136 was rated at 13W into 8R so it should be possible to find suitable TOP66 (TO220) types.
I can't find suitable local types retail, though I'd be tempted to try TIP41/42B or C, if all else and common sense failed. Perhaps someone else would know a common TO220 pair that will run up to 25V rails and deliver 20W/4R?
I
Here is an older thread that answers your questions but doesn't give you the antiques.
http://www.diyaudio.com/forums/solid-state/56192-fairchild-find-print.html
So you aren't the first to come up against TO66 power transistor problems. You'll see that no data sheets are availaabke for them but if you really want to know, perhaps Leo Simpson at Silicon Chip will assist, After all, it was his baby, AFAIK;
The TOP-66 plastic power types were developed to replace them wayback-even then. These will fit into the same holes if you trim off the collector lead and attach with the appropriate mounting bolt. I assume you can identify the connections of both original and replacement types. Don't forget to insulate with a new mica and grease, perhaps the old bush is OK.
What you need is a complementary pair (don't iust swap the bad one) that meets the AY9171/8171 pair spec. 35W output is max. rating. I believe the 136 was rated at 13W into 8R so it should be possible to find suitable TOP66 (TO220) types.
I can't find suitable local types retail, though I'd be tempted to try TIP41/42B or C, if all else and common sense failed. Perhaps someone else would know a common TO220 pair that will run up to 25V rails and deliver 20W/4R?
I
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Thanks Ian,
I'd not heard of the TOP-66 cases so I'll follow that up tomorrow. There seems to be a fair bit of open loop gain in this so a difference in output transistor Hfe etc may not be significant between the two channels, but totally agree need to replace the pair, otherwise distortion and Q-point will be unacceptable.
I may also try to contact the OP of the thread you gave in the hope that he may still have the transistors and has not built them into anything or junked them (!).
Appreciate the thoughts you gave
cheers
Anton
I'd not heard of the TOP-66 cases so I'll follow that up tomorrow. There seems to be a fair bit of open loop gain in this so a difference in output transistor Hfe etc may not be significant between the two channels, but totally agree need to replace the pair, otherwise distortion and Q-point will be unacceptable.
I may also try to contact the OP of the thread you gave in the hope that he may still have the transistors and has not built them into anything or junked them (!).
Appreciate the thoughts you gave
cheers
Anton
Ian,
You've given me yet another useful course to pursue. At first blush the MJE3055T/2955T would fit electrically so with their TO220 format I would just need to find a way of mounting them on the existing heat sink - maybe by dividing the heatsink into two parts insulated from each other, I'll look at the circuit tomorrow too, as the present pair is mounted on a common heatsink.......
Thanks again
Anton
You've given me yet another useful course to pursue. At first blush the MJE3055T/2955T would fit electrically so with their TO220 format I would just need to find a way of mounting them on the existing heat sink - maybe by dividing the heatsink into two parts insulated from each other, I'll look at the circuit tomorrow too, as the present pair is mounted on a common heatsink.......
Thanks again
Anton
TO(P) substitutes
Actually, TO(Plastic)66 = TO220 and the idea was always to trim or peel back the collector pin, bend the others down and poke them in the B & E holes so the collector tab hole lines up with the nearest mounting hole - easy and intended to be so. TOP3 (sort of TO247) is the same deal for TO3 transistor substitutions.
Add new mica (original micas were cut with guide pin position notches to match) and add some grease and you're good to go.
You'll probably realise some sleeving is needed in the heatsink lead holes and a bit o silicone rubber is ideal as PVC tends to fry.
Have fun digging out a seven year old post
Actually, TO(Plastic)66 = TO220 and the idea was always to trim or peel back the collector pin, bend the others down and poke them in the B & E holes so the collector tab hole lines up with the nearest mounting hole - easy and intended to be so. TOP3 (sort of TO247) is the same deal for TO3 transistor substitutions.
Add new mica (original micas were cut with guide pin position notches to match) and add some grease and you're good to go.
You'll probably realise some sleeving is needed in the heatsink lead holes and a bit o silicone rubber is ideal as PVC tends to fry.
Have fun digging out a seven year old post
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Ian,
Both the MJE3055T and MJE2955T appear to be available so I'll order some from RS-online. Looking at the circuit this morning, both collectors connect together, so both can be bolted to the heatsink with impunity (and suitable bolts and grease), as were the TO-66 devices before them.
The speaker connects between this point and earth, with a 150ohm resistor bleeding across it presumably to tie it down a bit dc-wise when the speaker is not connected. That tells me I need to ensure that the transistors are balanced so there is no DC voltage at this point; this may need some tweaking to component values earlier in the five-stage direct-coupled circuit with feedback stabilisation. Fun and games ahead even with the new devices!
Thank you so much for your patience and information.
cheers
Anton
Both the MJE3055T and MJE2955T appear to be available so I'll order some from RS-online. Looking at the circuit this morning, both collectors connect together, so both can be bolted to the heatsink with impunity (and suitable bolts and grease), as were the TO-66 devices before them.
The speaker connects between this point and earth, with a 150ohm resistor bleeding across it presumably to tie it down a bit dc-wise when the speaker is not connected. That tells me I need to ensure that the transistors are balanced so there is no DC voltage at this point; this may need some tweaking to component values earlier in the five-stage direct-coupled circuit with feedback stabilisation. Fun and games ahead even with the new devices!
Thank you so much for your patience and information.
cheers
Anton
Hi Anton,
You could also try contacting Tinkerbell (No seriously!)
They had full kits of transistors for this amp.
http://www.diyaudio.com/forums/solid-state/56192-fairchild-find.html
Cheers, Ralph
You could also try contacting Tinkerbell (No seriously!)
They had full kits of transistors for this amp.
http://www.diyaudio.com/forums/solid-state/56192-fairchild-find.html
Cheers, Ralph
Thanks also for the design info. It would seem to be CFP, presumably with emitter resistors to the rail end. as once was common practice. Of course, anything could be the case back then in early days of silicon power.
An interesting snippet is that this and a larger design, was based on a package deal (literally, a sealed printed plastic packet set) of the semis from Fairchild Australia. This was sold relatively cheaply which ties in with the comments Jackinnji made in the old thread about the Fairchild-Natsemi changes back then. (obsolete stock)
I never built this one, so I didn't take an interest in my early twenties then and repaired only minor things on a couple since. I'm interested now to learn the topology (i.e. do the drivers connect to the output bases via their collectors or emitters?)
I shouldn't guess whether the input was an LTP or not. Otherwise I'd suggest to add offset adjust via a pot. fitted in place of any emitter degen. resistors. As US product, I would think it based on their app, notes, I'd say so rather than the British CE, single transitor design from Mullard days.
'Would appreciate your comment.
An interesting snippet is that this and a larger design, was based on a package deal (literally, a sealed printed plastic packet set) of the semis from Fairchild Australia. This was sold relatively cheaply which ties in with the comments Jackinnji made in the old thread about the Fairchild-Natsemi changes back then. (obsolete stock)
I never built this one, so I didn't take an interest in my early twenties then and repaired only minor things on a couple since. I'm interested now to learn the topology (i.e. do the drivers connect to the output bases via their collectors or emitters?)
I shouldn't guess whether the input was an LTP or not. Otherwise I'd suggest to add offset adjust via a pot. fitted in place of any emitter degen. resistors. As US product, I would think it based on their app, notes, I'd say so rather than the British CE, single transitor design from Mullard days.
'Would appreciate your comment.
I built one back in late '74 or early '74 (and by jingos I did a rough job!) but I seem to remember that both collectors connected to the heatsink with no insulating washer so it must have been a CFP setup. Would be interesting to see the circuit after all these years.
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