30 years on
My stereo has had various components replaced over the years; speakers, CD players, cassette decks, record decks, tuners. One part has remained in use for 30 years - the amplifier. It is one I built and is an E.A Rule design called the PW Winton, that featured in the March 1979 issue of Practical Wireless. I have only had to repair it once when a coupling capacitor dried out and went noisy. A very reliable amp, thanks mainly to the output stage using complimentary Hitachi power MOSFETS (2SJ48 and 2SK133).These devices have a negative temperature coefficient so there is no risk of thermal runaway. When I get time I will scan the article and put it online.
21/9/2015 07:40:02 pm
Hi, Just come across you comments. I was the designer of the Winton and it was reviewed by Gordon King but the review wasn't published until a few years after it was in PW. At 86 years I am still designing but mainly aerials for amateur radio. I may have a copy of the review so if you contact me I will look it out and scan it.
22/9/2015 06:52:20 pm
22/9/2015 08:16:01 pm
23/9/2015 10:11:54 am
I have never seen a review. Thanks in advance for sending the one you have.
4/3/2017 04:50:56 pm
Amazed to find this string of comments. Ten of us got together here in Christchurch, NZ. Some built cabinets, some organised components, some the toroidal transformers, some the circuit board ... most built their own circuit up. This was all mid-late 1970's?
5/3/2017 01:15:00 pm
Wow. just been hunting round for what the class for the Winton PW is. Class A or Class AB.
6/4/2018 10:54:38 am
15/6/2018 05:34:03 am
I built just the power amp stage of the Winton amplifier about 30 years ago. Through the years I made several successful modifications. It was pleasure to have that amp in the system and
4/7/2019 06:34:39 pm
Hi there - Richard - I think we know each other from Greymouth? Great to see the designer of the Winton amp posting here. I have heard a lot of amplifiers and also have a lot of amplifiers, mainly from Sansui, including the high-speed output AU-X1, and a lot of kit VFET amplifiers. I was rummaging around in my sisters basement and found one of these Winton amps. OI was about to dismiss it until I saw the FETs on the back panel. Opening it up - saw heaps of polystyrene caps inside. This convinced me this amp was worth resurrecting. I found the PW mag mack issues and checked all the voltages. A couple were off but not by much. A full recap (some with Nichicon FG, and also putting metal film resistors in the signal path, as well as bypassing the main PS caps and also - changing all three original opamps for modern OPA2134's. Fired it up - setup was easy. I am running the bias a bit hotter at about 90mA - as some of my voltage measurements werent high enough at the outputs. Fired it up and my jaw hit the floor. If you have one of these - restore it, my thread is here: https://audiokarma.org/forums/index.php?threads/help-with-1979-fet-output-integrated-amplifier.870787/page-2#post-12803441. This amp is incredibly special and I cant stop listening to it. You certainly designed something very special here Edward!
8/10/2019 09:50:27 am
Wow, so cool to find this thread! I found one of these at the tip shop in Wellington. I'd ignored it (as everyone else had) a few times but decided one day to have a look and the cover slid right off to reveal that big torroidal transformer, massive power caps and other quality components.
8/10/2019 12:19:58 pm
Re: the hum issue - Id check the trafo mounting to ensure it is tight and also put in some rubber grommets or sheeting to isolate mechanical noise from it to the chassis.
26/11/2020 08:46:48 pm
My Winton is still in daily use. I have not changed anything within it since I replaced all the resistors in the phono section with close tolerance low-noise versions over 30 years ago.
27/11/2020 02:43:16 am
Electrolytic capacitor deteriorate in time. Assuming just mildly warmed ambient, 20-30 years are enough time for noticable degradation of performance. In extreme cases may lead to capsule rupture. Therefore re-capping rejuvenates the amp a bit.
27/11/2020 04:29:10 am
Petar, thanks for this. I'll give it a go. Is it just the electrolytic capacitors that need replacing, or should I aim to replace all of the capacitors?
27/11/2020 08:03:56 am
Absolutely - replace all capacitors, but only the electrolytic ones. Use the service data as a guide. The total cost will be minimal. Just ensure that you use good ones (ie: Panasonic FC/FR types). Ensure voltage ratings are the same or greater than what you are replacing, ensure polarities are correct. All the old magazines for original build guides are online in an archive somewhere.
28/11/2020 02:00:19 am
Non-electrolytic capacitors are much more durable and need no replacement.
28/11/2020 02:27:58 am
Petar and Simon, I have the original magazine and the kit assembly instructions, so when I get time I'll order some new electrolytic capacitors. I would not have known that the power supply capacitors could be replaced by higher values, so thanks for this extra tip.
28/11/2020 04:51:48 am
Higher value of the power supply capacitors is always better for clearer supply voltage. BUT, high capacitance puts strain on the bridge rectifier and the transformer, mostly on power-up. So some caution is commended. However I think 10000uF isn't too much. In the '80s, price and physical size were major constraints so 4700uF was considered good enough.
28/11/2020 05:15:08 am
One thing that has always puzzled me is that when I switch the Winton off there is a rumble/thump noise through the speakers unless I turn the volume to zero. I automatically turn the volume to zero without thinking about it these days, but if this is something that could be stopped I would be interested in hearing people's views. If it's the power supply capacitors discharging, then would increasing the capacitors' size exacerbate the problem or reduce it?
28/11/2020 08:19:32 am
This thump comes from the preamplifier part to which I'm not familiar. I built only the power amplifier part as a stand alone unit.
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