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Author Topic: Old Aussie Jade Amplifier  (Read 2673 times)

phatt

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Old Aussie Jade Amplifier
« on: March 22, 2015, 08:36:40 AM »
Here is and old Aussie SS rig from way back, came to me with dead poweramp.
Hey surface mount "old style" Which does actually make working on it quite easy in some ways. :tu:

After firing up with new parts I became concerned about that broken PCB which is only held in place by the power transistor sockets and a lump of foam glued on the back of the floating pcb so I added some extra stand offs for support.

The speaker wire is/was hard wired to top corner of pcb track with no other clamp or support so any hard reef on the speaker cable would just snap the pcb which quite obviously has happened before and would likely happen again.
So looking at the vertical quad box that goes with the amplifier and a very short speaker cable,,, hum? I added a block connector and clamp at back of cabinet and added a longer speaker cable. Replaced a couple of dud pots and All fixed now.

I thought I'd post this because I've not seen this track side mounting done before and also I traced the OD channel as it actually sounds quite good, very responsive. Just backoff the guitar volume and it cleans up quite nice.
It's never going to put heavy metal rigs out of work but through the Quad box it does a convincing rock sound.

Any comments on the poweramp design are welcome as I've not seen this type before and I'm wondering if it's any good,, pro's and con's?
Cheers, Phil.

Roly

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Re: Old Aussie Jade Amplifier
« Reply #1 on: March 22, 2015, 11:44:04 AM »
Thanks phatt, gone into the AVA in-tray.  :dbtu:



{Ya'know, I have a funny feeling looking at that broken PCB splint job and pile of 5W resistors  ??? ... I'm not going to dig back through my job sheets, would have been more than ten years ago, but I have a funny feeling ... I don't remember no quad box, but there was a time when amps were coming in from very far afield, Brisvagas to Sinny.  What location did you pick this up, NSW somewhere?  There might be a "RR-squiggle, date" in pencil on it somewhere.}
If you say theory and practice don't agree you haven't applied enough theory.

phatt

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Re: Old Aussie Jade Amplifier
« Reply #2 on: March 24, 2015, 09:09:55 AM »
Hi Roly,
        Yes I figured you would have likely seen one of these in your travels. No I did not notice any signature.
This chap is a drummer in his 80's and just plays His Vinyl collection through it now but told me he has owned it for many years and made the mistake of loaning it out which is when the board got broken. It came with 2 speaker cables (one short ,one long) and as the quad box is already 4- Ohm I'd say someone has added another speaker so with no output protection it would have fried the output. :-X
Hence I removed the short speaker cable. 8)

The chap lives in Lakes Entrance Victoria and did a lot of old time dance band gigs around these parts.

I'm now living up the road in Bairnsdale which is the hub for East Gippsland but busting to get back up north. The cold is bad enough but add the incessant wind down here and it's no place for a Queenslander who is used to wearing a T shirt and sandals for most of the year.  :'(

The schematic should be fairly close to what is on the board. The power amp voltages are taken from the working circuit and were within a few mV of the simulation.
I'm getting better at this repair game but have to watch what I take on as it's easy to get lost even with simple circuits.
Phil.

Roly

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Re: Old Aussie Jade Amplifier
« Reply #3 on: March 24, 2015, 11:35:51 AM »
Well none of that fits, Lakes Entrance is way out of my normal orbit, but I certainly have a memory of splinting that very broken circuit board (and something about that screw next to the break, flimsy for some reason (?) ) ; would have been in the Manning River area and around ten years ago, maybe more.

{now I guess I won't be satisfied until I dig out and search back through my records to put my mind at rest - I fixed a lot of brummy gear for bands and musicians just passin' through.}

Quote from: phatt
I'm now living up the road in Bairnsdale

Be thankful it's not Moe. ;)  We had a fall of snow here in Creswick last winter (but then I once had a fall of snow when I was inland of Taree).  I love the warm and the wildlife, but the ticks are a real bringdown.
If you say theory and practice don't agree you haven't applied enough theory.