Speakerplans.com Homepage
Forum Home Forum Home > General > Amp Forum
  New Posts New Posts RSS Feed - PPX1200 humming
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

PPX1200 humming

 Post Reply Post Reply Page  <12
Author
Message
scott_fury View Drop Down
Registered User
Registered User


Joined: 28 October 2012
Location: Bristol
Status: Offline
Points: 319
Post Options Post Options   Thanks (0) Thanks(0)   Quote scott_fury Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2020 at 10:09am
Originally posted by kedwardsleisure kedwardsleisure wrote:

I've had plenty where the led just snaps off.
Another good one is where someone has taken the front panel off to clean it or whatever and when they've put it back they've bent the LED out of the way so it doesn't shine through.
And they do just fail.

ZTX super e-line transistors are very good, developed by uk-company Ferranti no doubt for some cloak-and-dagger application. They just don't get on well with amplifiers!

Hopefully it’s something simple, but old sod and his law has a habit of introducing himself when I work on stuff. Currently have 4:1 ratio of fixing and breaking things, so doing good at the moment. Fingers crossed.

I assumed they were the sort of things that would turn up inside my old Commodore 64, but ‘cloak and dagger’ sounds way more interesting than enabling teens of the 80’s to play International Karate +.
Back to Top
Sonic the hedge View Drop Down
Registered User
Registered User


Joined: 12 May 2020
Status: Offline
Points: 161
Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic the hedge Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2020 at 2:58am
Originally posted by scott_fury scott_fury wrote:

Also, I assume that they won’t test a component on a board, and I’m hoping I can test these transistors without having to pull out the board and unsoldering them if they’re still good?

I find the problem with testing 'on board' is it's often hard to tell if you are getting an (in)accurate reading due to other components on the PCB in parallel etc.

Albeit heatsinked transistors can be tedious to remove screws and nuts so it's easier to isolate the transistor for testing 'on board' by disconnecting surrounding components. Resistors and wire links are my favourite cos you can desolder just one end and leave it flying.

Anything else should come off the PCB easily with a solder sucker, asuming
it's old through-hole stuff with real lead solder, but we are talking PPX Tongue

One of the best sounding, most robust amps ever built IMHO. All the more amazing since Citronic was aimed at the 'Disco' sector.


Edited by Sonic the hedge - 20 May 2020 at 7:09am
Back to Top
scott_fury View Drop Down
Registered User
Registered User


Joined: 28 October 2012
Location: Bristol
Status: Offline
Points: 319
Post Options Post Options   Thanks (0) Thanks(0)   Quote scott_fury Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2020 at 8:12am
Originally posted by Sonic the hedge Sonic the hedge wrote:

I find the problem with testing 'on board' is it's often hard to tell if you are getting an (in)accurate reading due to other components on the PCB in parallel etc.

Albeit heatsinked transistors can be tedious to remove screws and nuts so it's easier to isolate the transistor for testing 'on board' by disconnecting surrounding components. Resistors and wire links are my favourite cos you can desolder just one end and leave it flying.

Anything else should come off the PCB easily with a solder sucker, asuming
it's old through-hole stuff with real lead solder, but we are talking PPX Tongue

One of the best sounding, most robust amps ever built IMHO. All the more amazing since Citronic was aimed at the 'Disco' sector.

Thanks for the tips. I think my issue is just a lack of experience. I’ve been a domestic electrician, auto-electrician, can mig and tig weld..... but I can’t solder without ballsing things up. Just can’t seem to hang of it. Got a suction tool and a couple of different wattage irons. Tried making basic circuits, bat detectors etc :) Can’t do it. The idea of replacing a component on a circuit board gives me a bit of the fear! I shall perservere as I really want to do it, but may need a dummy item to practice on first 😅


Edited by scott_fury - 20 May 2020 at 8:12am
Back to Top
Sonic the hedge View Drop Down
Registered User
Registered User


Joined: 12 May 2020
Status: Offline
Points: 161
Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic the hedge Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2020 at 8:27am
Originally posted by scott_fury scott_fury wrote:

Thanks for the tips. I think my issue is just a lack of experience. I’ve been a domestic electrician, auto-electrician, can mig and tig weld..... but I can’t solder without ballsing things up. Just can’t seem to hang of it. Got a suction tool and a couple of different wattage irons. Tried making basic circuits, bat detectors etc :) Can’t do it. The idea of replacing a component on a circuit board gives me a bit of the fear! I shall perservere as I really want to do it, but may need a dummy item to practice on first 😅

Yeah practice is the key, I have been buggering up electronics since I was a kid LOL

Defo worth getting some old knackered hi-fi etc just to practice soldering on, you may well find that taking away the fear of breaking something actually improves your confidence and technique quite quickly.


Edited by Sonic the hedge - 20 May 2020 at 8:45am
Back to Top
jbl_man View Drop Down
Moderator Group
Moderator Group
Avatar

Joined: 12 January 2005
Location: London.
Status: Offline
Points: 11154
Post Options Post Options   Thanks (0) Thanks(0)   Quote jbl_man Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2020 at 9:09am
One thing i would mention, even after completely de-soldering components on these old Citronic amps,they were very tightly fitted,(they stay in place firmly without any solder at all), it's almost like pulling teeth. 
Be seeing you.
Back to Top
Sonic the hedge View Drop Down
Registered User
Registered User


Joined: 12 May 2020
Status: Offline
Points: 161
Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic the hedge Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2020 at 10:46am
Originally posted by jbl_man jbl_man wrote:

One thing i would mention, even after completely de-soldering components on these old Citronic amps,they were very tightly fitted,(they stay in place firmly without any solder at all), it's almost like pulling teeth. 

Are the legs folded over to hold them in? That can be a b@stard! 

With practice you can heat the solder, bend the leg straight and push it through the board, all in one go using the tip of the iron. Use a small angled tip, use the tip like a wedge/lever to lift the leg, then a slight twist of the tip to push the leg through the board. Obviously for transistors, ICs etc. need to straighten all the legs before it will come out. 

Probably not best advice for a complete novice though! Have to be quick so you don't overheat the component.


Edited by Sonic the hedge - 20 May 2020 at 2:04pm
Back to Top
scott_fury View Drop Down
Registered User
Registered User


Joined: 28 October 2012
Location: Bristol
Status: Offline
Points: 319
Post Options Post Options   Thanks (0) Thanks(0)   Quote scott_fury Quote  Post ReplyReply Direct Link To This Post Posted: 01 June 2020 at 8:06am
So I got the 1600 out last night to test the transistor for this clip LED, but unfortunately noticed something was wrong with one of the transformers. 

The glued piece in the centre of the coil has broken and the coil is now loose. I have looked at the 1200 schematics and I can see there is a 125degree trip labelled on the transformers which i guess is a thermal cut out. It looks like the trip and transformer are all glued to mounting bolt? 


I’m going to test it today to see if it still works as it should, but is it possible to glue this back together, and if so, which glue would do the best job...... some sort of 2-part araldite maybe?
Back to Top
kedwardsleisure View Drop Down
Old Croc
Old Croc


Joined: 20 January 2009
Location: Staffordshire
Status: Offline
Points: 4938
Post Options Post Options   Thanks (0) Thanks(0)   Quote kedwardsleisure Quote  Post ReplyReply Direct Link To This Post Posted: 01 June 2020 at 11:22am
I think originally it would be a 2-part epoxy or polyurethane hard potting compound. Is that the reason yours was buzzing?

I've used polyester filler in an emergency for the big transformers in the past.



https://www.rapidonline.com/robnor-px804c-bk-500g-potting-compound-twin-pack-500g-87-0216
Kevin

North Staffordshire

Back to Top
scott_fury View Drop Down
Registered User
Registered User


Joined: 28 October 2012
Location: Bristol
Status: Offline
Points: 319
Post Options Post Options   Thanks (0) Thanks(0)   Quote scott_fury Quote  Post ReplyReply Direct Link To This Post Posted: 01 June 2020 at 11:53am
Thanks for the link. I imagine it’s easy enough to stick the trip back to the bolt, but getting something to stick to the coil covering may be a little tricky.

I imagine it had a knock upside down maybe. I don’t know if this sort of thing is common but I’m going to have to be more vigilant in the future. 

Originally posted by kedwardsleisure kedwardsleisure wrote:

Is that the reason yours was buzzing? 

Nope. This is the 1600. The 1200 was buzzing.
Back to Top
kedwardsleisure View Drop Down
Old Croc
Old Croc


Joined: 20 January 2009
Location: Staffordshire
Status: Offline
Points: 4938
Post Options Post Options   Thanks (0) Thanks(0)   Quote kedwardsleisure Quote  Post ReplyReply Direct Link To This Post Posted: 01 June 2020 at 1:02pm
might be worth opening a new thread for a different amp so it avoids confusion in the future
Kevin

North Staffordshire

Back to Top
 Post Reply Post Reply Page  <12

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.06
Copyright ©2001-2023 Web Wiz Ltd.

This page was generated in 0.125 seconds.