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PPX idle warm up time |
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GregM 
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Joined: 13 December 2009 Location: NE Hampshire Status: Offline Points: 525 |
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 Topic: PPX idle warm up timePosted: 29 March 2012 at 7:13pm |
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Guys,
It's been a very (very) long time since I had any PPX amps in my stable, and at my age, the memory doesnt work too reliably anymore!......
I wanting to know whether the cooling fan and thero trigger in my PPX450 are actually working, and until Sunday I'm not going to get a chance to plug it in a source and pair of speakers so I'm just sitting here with it powered up idling, getting quite warm and wondering why I can't remember how warm they get before the fan should cut in....
Can anybody advise (Ian?) approximately how long after powering up and idling they are warm enough to trigger the fan?, obviously I don't want to wait too long only to discover the fan's stuffed, and I've let it toast itself, but equally, I'm inpatient so don't want to wait until Sunday!!
New toys eh?, tsk!
Greg
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Mhamplification
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Joined: 16 July 2009 Location: County Durham Status: Offline Points: 541 |
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Posted: 29 March 2012 at 8:17pm |
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Greg
The fan should come on and run for a couple of minutes then switch off again It depends how the bias is set as to how long it takes till the fan should come on, maybe 5-10 minutes is the norm. Might be best to bypass the thermal switch to check it is working properly, a lot of the fans in older PPX amps are 115 volts so don`t hardwire it to the mains. You can wire it via the mains transformer primary windings to get 115 volts Let us know how you get on Good to see you have a ""decent amp"" in your collection now Martin |
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GregM
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Joined: 13 December 2009 Location: NE Hampshire Status: Offline Points: 525 |
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Posted: 29 March 2012 at 8:53pm |
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Thanks Martin,
Useful to know the early ones had 115v fans, I'll bet that's caught out a few dabblers!
The machine got rather warm just idling for about 25 mins, and no sign of the fan firing up, so I've powered off until I have the time to poke about which won't be until the weekend.
I'll definitely try bridging the thermo unit as a start - assuming I can find it. I'm downloading the schematic at the mo so hopefully it's quite obvious. Seems a very long time since I opened up a PPX.
Regards,
Greg
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jbl_man
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Posted: 29 March 2012 at 9:25pm |
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That doesnt sound right Greg,as Martin says,the fan should trip-on after around 5 minutes at idle.
The trip is a thermal switch mounted on the heatsink next to the Hitachi mosfets. |
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Be seeing you.
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GregM
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Posted: 29 March 2012 at 9:46pm |
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Hmmm, that was what I feared, I had a distinct feeling from what I'd read here in the past the fan would cut in reaonable quickly.
I just hope a possibly dead fan hasn't allowed it to over cook in the past, I won't get to dig into it until Sunday. Seller (yep, on SP
 ) sold it as fully working, and actually confirmed having tested it the morning before i was due to collect it so I maybe just looking at a duff fan. Fingers X'd.Cheers Ian for the pointer - I'm sure the trip will become obvious.
Greg Edited by GregM - 29 March 2012 at 9:54pm |
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jbl_man
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Posted: 29 March 2012 at 9:56pm |
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Should be ok,on the heatsink there are two thermal switches,one trips the fan at 60* if i remember,and the other switch is a thermal cutout at 90*,which should protect the devices...there is also another thermal trip on the transformer as well,which shuts the power off if the transformer overheats.Quite well protected these amps!
Just checked mine,def. 115v fan. |
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GregM
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Posted: 29 March 2012 at 9:58pm |
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Good man, thank you.
Good old fashioned engineering eh?, protection ruled the way!
Greg
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jbl_man
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Posted: 29 March 2012 at 10:05pm |
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You can see one switch at the far end of the heatsink inline with the output devices,the other switch is other end of of heatsink.(hidden by the fan in ths photo)
Edit,this is a 900,but layout is same in 450.  Edited by jbl_man - 29 March 2012 at 10:08pm |
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VSS
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Joined: 28 December 2011 Location: Belgium Status: Offline Points: 87 |
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Posted: 29 March 2012 at 10:14pm |
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Fan is 115 V . I replaced one in one of my ppx 900 . If I'm not mistaken the fan runs continiously from the moment the amp is switched on ( ppx 900 ) . Anyway , mine are .
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GregM
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Posted: 29 March 2012 at 10:15pm |
Except that one's also got nice handles!
 Thanks again Ian - I know what I'm looking at now - and can also see the tranny thermal cut out too.
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GEB
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Joined: 13 November 2009 Location: East Midlands Status: Offline Points: 2052 |
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Posted: 29 March 2012 at 10:20pm |
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Stick a 240v fan in, wire it up to be on full wack 100% of the time?
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GregM
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Posted: 10 April 2012 at 8:57pm |
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Update time - just in case anybody was actually following the story of my migration back from HH to Citronic.....
Despite being filthy inside and out, it works!, both channels pump away, although channel B did seem a tad quieter in my very untechnical test.
The fan switch (presumably a thermistor?) did have an intermittent fault, there was what I guess was a dry joint/fractured cable at the heatsink end - a quick strip back and resolder and the fan pops in and out every 5-6 mins as you guys suggested it would.
I do need to spend a fair bit of time cleaning it out and tidying up the casework - (oh, and finding some front handles!), then it'll find a new job which may just become a core part of my home hi fi
 Martin - out of curiousity, would you happen to have a full copy of the service manual and schematics for the PPX450 I could see?, I really fancy seeing how much of my ancient BBC training I could remember - then, when I bugger it up I can add the PPX to the pile of kit waiting to find their way to you for service and/or repair!!
Greg
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jbl_man wrote: