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RRV-10
Silver Member
Australia
246 Posts |
 Posted - 03/18/2007 : 06:25:08
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| I got my PSA for free with a PS-2 - it's a vintage 80s unit with a grey tip and thankfully held together by screws. Inexplicably it hasn't been working lately so I opened it up this afternoon and there's a little fuse in there that's blown. I've jotted down the info 250v500ma but anyone want to offer any advice before I head over to the electronics store? |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 03/18/2007 : 07:33:21
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Hi RRV-10
Buy more than one fuse, in case the regulator or has a fault,
IF you have a meter check the resistance of the transformer
Both on the mains side, and on the secondary side, in case it's shorted
the Primary will be under 100 or so ohms
The secondary will be very low resistance.
Is the fuse on the primary or on the secondary side.
if it's on the primary, you will have to mesure the primary of transformer, after the fuse, as it's open.
I believe the PSA has a 7809 9Volt 3 Pin regulator on the secondary.
also visually inspect the filter capacitor near the 7809 this is sometimes labeled LM7809 or some other prefix.
If your not sure, post up a pic or two, or PM me, you have my details from previous emails.
Regards Dr.Bob
PS if it's the 7809, you could get a 7808 at a pinch, but you will be 1 volt low, like a slightly flat battery.
Email me anyway, if you get stuck, you know I stay up late.
Jaycar have 7809 & sometimes Dick Smith
BTW I have a heap of 500mA fuses if you get really stuck, is it the 20mm by 5 mm size ? these are called M205 fuse size fuses, the larger ones like you see in cars are called 3AG size
Hope this all helps.
If you are anywhere around the Danadenong Sth area I could donate you some.  it's close to where I work.
If I remember, you are situated, around the Rowville/Knox area.
Regards Again Dr. Bob |
Edited by - Dr. Bob on 03/18/2007 07:33:54 |
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RRV-10
Silver Member
Australia
246 Posts |
Posted - 03/19/2007 : 02:22:30
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Thanks for all the help Bob. It was kind of hard to get a consistent reading on the mains side but it was hovering between 130-150, whereas on the secondary it was around 5. Here's a pic of the guts
The fuse is the first thing in the circuit after the transformer. You can see its socket on the far right. Fuses do go after a while don't they? I'll replace it and see what happens. If it blows again then we'll know there's something else wrong. I can't see what the regulator has written on it as its facing the capacitor. Thanks for the offer of the fuse, but I don't make it down to Dandenong all the often  . I'll see if I can find time to get into a Dick Smith today.
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 03/19/2007 : 07:20:08
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Hi RRV-10
If you have no luck & can't fix it, mail me.
We'll see what we can arrange.
Regards Dr. Bob
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RRV-10
Silver Member
Australia
246 Posts |
Posted - 03/19/2007 : 12:24:53
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| Hi Bob. The PSA is fine. I threw a fuse in there and it's pumping out 9.7v. I connect it to my half-working homemade LBP1 and bam - the fuse has blow again. I guess the LPB1 isn't grounded correctly *sigh* Anywho, the PSA is now connected to the Maxon delay. Actually I think it may sound ever so slightly sweeter running at 9.7v compared to the 9.1v of the other adapter. Thanks for the help. |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 03/19/2007 : 12:50:41
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quote:
Originally posted by RRV-10
Hi Bob. The PSA is fine. I threw a fuse in there and it's pumping out 9.7v. I connect it to my half-working homemade LBP1 and bam - the fuse has blow again. I guess the LPB1 isn't grounded correctly *sigh* Anywho, the PSA is now connected to the Maxon delay. Actually I think it may sound ever so slightly sweeter running at 9.7v compared to the 9.1v of the other adapter. Thanks for the help.
Anytime RRV-10
Sounds like your DIY - LBP1 has a short on the DC input jack, re-check your wiring, you may have missed something.
Regards Dr. Bob
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whurly
Copper Member
Australia
37 Posts |
Posted - 04/13/2007 : 02:38:01
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| I've just blown a second fuse on my PSA, it sounds like this might be a common problem. It's frustrating because when it works the PSA is a clean supply - my benchmark is getting no hum from my DE-7. I'm a big fan of the Dano Hum Eliminator adaptor but it's impossible to buy these separately (in Australia at least). I actually bought a Dano Pastrami OD just to get the adaptor that came with it! |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 04/13/2007 : 10:16:40
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quote:
Originally posted by whurly
I've just blown a second fuse on my PSA, it sounds like this might be a common problem. It's frustrating because when it works the PSA is a clean supply - my benchmark is getting no hum from my DE-7. I'm a big fan of the Dano Hum Eliminator adaptor but it's impossible to buy these separately (in Australia at least). I actually bought a Dano Pastrami OD just to get the adaptor that came with it!
Hi whurly
You might have to replace the large filter capacitor inside the PSA.
these filter caps dry out with heat & age.
I replace many such filter caps, inside plug packs that can be opened.
I replace many (And I do mean many) every month.
the plug packs are running 24-7 so they last about 1 to 2 years, befor I see them back in for a new filter cap.
And it does get quite hot inside these units, they get hotter, the more current you draw from them.
Not to mention that some of the PSA ACA adapters, are getting very old in the tooth.
I'm surprised that a lot more of you guys don't have PSA's with faulty dried out filter caps.
The correct Technical terminology, is High ESR
ESR stands for Equivalent Series Resistance.
If you PSA hums even just a little, and you can open it, change the filter cap.
Or it might be just, that one of your pedals is starting to play up, or has a broken-loose wire in it.
Also see if the nuts holding the pots, have come loose, & the pots might have rotated slightly, just enough to create a problem.
I find a that a lot of the old pedals that I get, have loose nuts on the pots.
(Hey Strato, no silly comments from you about loose nuts & pot shafts  )
see if you can isolate the pedal that is the culprit.
It might cost you a couple of new fuses.
whurly, can I ask you, to send a pic of a link to the Dano Hum Eliminator.
I couldn't find a link or Pic of it on the Web, just a 9V plug pack that they sell?
I'm guessing that hum from most PSA's is the filter cap, or a cold solder joint on the 9V 3-Pin 7809 regulator.
These Regulators have over -100dB of noise, that;s no noise, or hum.
Regards Dr. Bob
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My PSA blew a fuse...
