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Old 20th August 2006, 10:52 PM   #11
Michel is offline Michel  Canada
diyAudio Member
Join Date: Nov 2004
Location: L'Assomption, QC
Hello King,

There are not many things that can do this kind of problem in a P28.
If my memory is good there is not even a speaker relay in there which could be the cause.
The only things I can see is a dirty rca connector or the mono/stereo toggle switch that is inside.
A good cleaning with a quality product such as DeoxIT should cure hesitations.

One other thing, sometimes the fuse holders tabs get loose when they have had frequent careless fuse replacements.
I am not even sure it can happen with a P28 but if it is the case, all you have to do is remove the fuse
and press the tabs between your fingers until they nearly touch each other and put the fuse back.
I have seen that fuse holder tabs problem numerous times, especially with the ones that have the beige base.
The best way to avoid excessive stress to the tabs when replacing a fuse is to use a fuse puller.
The only one I recommend for that is the Ideal Industries 34-015.

Good luck!


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Old 21st August 2006, 01:12 PM   #12
mikeks is offline mikeks  United Kingdom
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Join Date: Jun 2004
Location: Animal farm
Default Re: Sugden P28 and P128

Originally posted by Michel
Sugden has always had the extremely bad habit of using capacitors that are too close to the working voltage. They do tend too to put resistors , transistors or zener diodes that radiates heat close to them...........

The other things that go wrong after the capacitors are the BC639 and BC640 drivers which have a little too much on their plate............

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Old 21st August 2006, 05:54 PM   #13
King is offline King  Canada
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Join Date: Aug 2006
Thank Michel, I will take a look tonight; however, sare there any possibly bad capacitors that might contribute to this problem.
BTW, my P28 has the heatsink at the back of the unit.
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Old 22nd August 2006, 01:57 PM   #14
King is offline King  Canada
diyAudio Member
Join Date: Aug 2006
Hi Michel and others, I open up the P28 last night, cleaned the
toggle switch with contact cleaner; and also discovered that indeed one of the 2A fuse holder was loose, so I squeeze the fuse holder with my fingers put the fuse back and now is fuse is tightly seating in place.

Since it was pretty late so I listen to it for may be 20 minutes, and so far no cutting in and out; hope it really resolved that problem.

I also got a reply from Sugden from England; they send me the A28II spec., they said the P28 use the same spec. only it's a power amp.
Stereo: 44 Watts/ch
Bridged: 95 watts

Question: How do you bridge the P28 to 95 watts mono?

Thanks again Michel, really appreciated your input.

Toronto, Ontario, Canada
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Old 22nd August 2006, 09:45 PM   #15
King is offline King  Canada
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Join Date: Aug 2006
Oh , Sugden (U.K.) also mentioned that the P28 is Class AB not
Class A; I always thought P28 is Class A !?
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Old 23rd August 2006, 07:07 AM   #16
AndrewT is offline AndrewT  Scotland
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Join Date: Jul 2004
Location: Scottish Borders
a far as I know the P28 is a high bias ClassAB (maybe a couple of watts of ClassA).
If the sinks look like my P128 they are far too small to support ClassA.
regards Andrew T.
Sent from my desktop computer using a keyboard
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Old 10th March 2008, 06:54 PM   #17
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Join Date: Mar 2008
Unhappy Sugden P28

Would you please send me the P28 schematic?

My P28 (heatsink on the side) went down and appears the fuzzy sound exactly the same as you mentioned in the thread. The fuzzy sound could last fuzzy sound 5 minutes and worked well initially. Now it comes fuzzy sound only without stop.

My technician (he is good at analog but I am more a digital guy) needs a schematic to examine not only capcitors also power transistors to close the two months mightmire on blindly check those components.

AAfter I read your post, we'd like to follow your suggestion to start over the examination of my P28 (capcitors and BC639/640 drivers) to avoid meassurement in the dark.

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Old 10th March 2008, 06:54 PM   #18
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Question Sugden P28 schematic

Can anyone send me a Sugden P28 schematic?
I am sticky on the fuzzy sound for two months. I really love this power AMP and need to repair its fuzzy sound.

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Old 10th March 2008, 07:24 PM   #19
Michel is offline Michel  Canada
diyAudio Member
Join Date: Nov 2004
Location: L'Assomption, QC
Hi Julian,

To fix a P28 with heatsinks on each side you need the A28B schematic.
Give me your email address and I will send it to you.
There are 5 parts marked by an asterisk on the parts overlay, make sure they are the value shown.
Do not hesitate to contact me if you need more help.


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Old 12th March 2008, 07:16 AM   #20
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Join Date: Mar 2008
Default Sugden P28 and A28B


Why do you refer A28B schematic for fixing P28? What is the background connection between these two models? P28 seems the successor of A28, correct?!

I'll check those 5 parts value with your suggestion after receiving the schematic.

Many thanks for the reminding
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