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Old 19th December 2011, 01:44 PM   #1
Butcher is offline Butcher  New Zealand
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Smile Playmaster Sixty-Sixty Stereo Amplifier SCHEMATIC

Hello! I was given this amplifer in payment for repairing a friends Ham Transceiver. I believe it was built about 1986 or so. Would anyone have a schematic for this amp? I believe Dick Smith may have sold it as a kit.

Another person tried to "repair" it by blanketly replaceing o/p and driver transistors which tested OK by me. They come in a we plastic bag.

I am hopeing to repair this vintage amplifier. Then modify it to improve the sound etc.

I have a Plinius 3 (1980) vintage amp that I have repaired (10 years ago) and recienty modified polyethylene caps, metal film resistors etc. It has two toroidal trannys.

Anyhow, I need another project to play with


Thanks guys.

Tony.
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Old 19th December 2011, 05:41 PM   #2
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Default EA 60/60 Integrated Amplifier Kit.

Hi Tony
No schematic that falls to hand at the moment, sorry, but it is a common EA and SC circuit of that era using a standard Hitachi design that first appeared with the introduction of Mosfets for the LTP with CCS and "balanced" VAS using TOI26 BF469/70 transistors. It uses MJE340/50 drivers with an MJ15003/4 complementary pair EF output - all on a full-size PCB with a C-core transformer PSU for 50V rails. It's very good for the age, very low noise (<-100dB) but needs a matched input pair badly. Arguanbly, it's EA's best design in bangs/buck

Bias is "optimum" 25mV and the Vbe multiplier, sensor, if TO92, gave assembly trouble. A mod using a joggled TO126 in the same location was the EA solution.

They are one tough and reliable amp, easy to work on and the RIAA MM input is a ripper with very low noise 2SC2545 LTP and NE5534AN. My amps are still going strong with original Philips main Electrolytics and other standard parts.

Expect trouble with the input selector switch, volume control mounting, pushbutton switch contacts and the relay operation as it is interlocked with the headphone socket switch which may need a bit of work to get the relay to operate correctly and switch the speakers on. It's a fancy but poor socket/switch and is insulated from ground intentionally.

If the power transistors are toast, it has been really abused !

Hang in if no one else can find a copy - I may still find it
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Old 19th December 2011, 11:17 PM   #3
glennb is offline glennb  Australia
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I have every issue of EA and can scan the articles. Let me know if you still require them.
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Old 20th December 2011, 08:03 AM   #4
Butcher is offline Butcher  New Zealand
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Thanks Ian finch!

You seem to know the amplifier well. I have been working on my Plinius 3. It has come up well.

I guess a "matched pair" would get the offset right (no DC at speaker terminals). My Plinius had blown o/p trannies, same type as the EA 60/60. I think people enjoy hooking as many speakers to there amp as possible. Me, I learnt that lesson years ago

Thanks for info about the idle current. My plinius I monified for DC offset. Installed a pot at one of the negitive feedback transistors supply. Was 50mV. Now is 0mV!

This made my left speaker happy!

Anyhow, thanks fellas, At least the amp doesn't use 2N3055, MJ2955. That was great news.

Also, diddn't know what the tranny was, "C" type. Cool, thanks!

I read about the "Cheep input switches" Least' me Plinius 3 doesnt have that problem (no bloody input switches! haha.

I am looking forward to getting the old girl going, she can live here elder years out in good hands. I found a circuit for the "Playmaster 40" dated 1976. has a bit in common.

The RIAA will come in handy with my (friends) old Technics record-player.

Guess the volume pot nut comes loose???

What the speaker relay do? Is it for the headphones? please explain if possible. I havent had the PCB out yet so...

If the tranny is good, will mod for seperate diode bridges and filter caps (havent had a close look yet so I could be talking rubbish!) Should inprove stereo seperation.

Will test o/p and drivers for leakage (shorts etc) and prob replace emiter resistors. Once I have it going. May post here the results.

I would love a copy of the article from EA glennb! It should be on the net for everyone to download (love the net for this reason)

Let me kno if you need help with anything glennb, and Ian finch thanks for takeing the time to publish the alignment info etc.

You Aussies are great, really!
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Old 20th December 2011, 10:49 AM   #5
glennb is offline glennb  Australia
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I would love a copy of the article from EA glennb! It should be on the net for everyone to download (love the net for this reason)
Let me kno if you need help with anything glennb, and Ian finch thanks for takeing the time to publish the alignment info etc.
You Aussies are great, really!
EA articles & errata have been scanned. Give me a day or so to crop and print to PDF and upload.
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Old 20th December 2011, 11:24 AM   #6
Butcher is offline Butcher  New Zealand
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Thanks Glenn. Please take your time.

One thing that I have learnt tonight, regarding modifying for better quallity, is a pair of diodes installed before the voltage-dropper resistors that supply current to the pre-amp section. At least on my Plinius 3. With the Plinius I will add these "isolation diodes". Also a 100uF 25V electro to assist the 100nF Poly!

I see that when the o/p stage is drawing loads of current, the preamp will be happy.

Thanks guys.

Tony.
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Old 20th December 2011, 05:02 PM   #7
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... I found a circuit for the "Playmaster 40" dated 1976. has a bit in common........Guess the volume pot nut comes loose???

What the speaker relay do? Is it for the headphones? please explain if possible.
Hi Tony
First, my error - mV should be mA bias current ( I have very poor specs too!)

The 40-40 has some similarities but not the balanced VAS or faster transistors

The closer design is the 2002 SC480 module which has been posted here on a few threads. It uses cheapest parts with 2 pair 2N3055/2955 varieties for it's utility purpose, but the rest is pretty much similar design. It's amazing what a few modern, matched semis can do for sound quality in this circuit, which is not far removed from a basic Symasym.

The speaker relay cuts the speakers off in the event of DC on the outputs, as could happen with a serious amp. fault. One of the headphone socket switches also drops the relay out by breaking power ground to it when the headphones are plugged in. Other switches then feed output to the tip and ring contacts of the headphones via the usual dropping resistors.

This has the benefit of avoiding flimsy rotary speaker switches and usually redundant controls but unfortunately, the socket switches became erratic. So it wasn't unusual to think the amp was dead but a few uses of the socket returned normal operation. Problems with the LORLIN or ALPHA moulded selector switch and stress of the volume control soldering to the PCB also made a frustrating experience when all and sundry used the amplifier. That was a case design issue as much as anything else.

Anyway, the schematic and description in the article(s) will clarify precise detail, but I have heard of people trying to repair this by fixing the amp. Well it wasn't broke - they just didn't understand the relay operation or what bad solder joints and oxidised contacts do.

It's hard to blow these as the small, perhaps 150VA transformer, sags the power supply and limits current into normal loads. Give it stiff supplies and I guess you would toast those mighty outputs like any silicon. It will pump 90WRMS, single channel, so it does have output and headroom well above it's nominal rating.
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Last edited by Ian Finch; 20th December 2011 at 05:16 PM.
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Old 20th December 2011, 11:51 PM   #8
Butcher is offline Butcher  New Zealand
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Thanks Ian Finch. I guess the o/p trannys are raded for 20 amps. Ine can solder at I think 285 degrees for 10 secs. The fuse might be 2 to 3 amps or so!. Your explination was the same as my conclusion! The person tried to fix the o/p when there was nothing wrong with it. The original trannys (Motorola) are dated 8631 (31st week of 1986). New ones are from memory 2004. This would have been when my friend received the amp. Haha, I guess he did a good job, for a novice! "Replace the biggest high power parts first" trick.

Well, it is amazing what one can conclude by just looking and seeing what was done. One can work out a probable cause or reason for falure.

Thanks for all the help. I researched the "C" tranny. Looks promising. Wish I had a second one!! To mod to dual tranny. Anyhow, there is no reason why an old amp cant sound magic after replaceing all the parts! Change carbon to film resistors. Remove all ceramic, replace with film caps, pref polyethylene or better Polystyrene. Beef up wiring to o/p. Heat sink bridge rectifier/s. etc.

Had my fair share of relay problems in ham radios. Strip of wet and dry sandpaper to the rescue!

Tony.
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Old 21st December 2011, 10:37 AM   #9
glennb is offline glennb  Australia
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EA articles & errata have been scanned. Give me a day or so to crop and print to PDF and upload.
http://dl.dropbox.com/u/44941643/Pla...r-60-60-v2.pdf
4.61 MB, 19 pages, scanned at 150 DPI, 256 greyscale
Copyright Federal Publishing 1986-1987
Reproduced for the purposes of fair research non-commercial use
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Old 21st December 2011, 02:51 PM   #10
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EA articles & errata have been scanned.
Excellent work, thanks glennb.
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