View Single Post
Old 23rd Apr 2012, 4:58 pm   #1
mark pirate
Dekatron
 
mark pirate's Avatar
 
Join Date: Mar 2008
Location: Worthing, West Sussex, UK
Posts: 5,185
Default JVC JA-S71 amplifier (1976)

I bought this amp second hand over 25 years ago to use as the heart of my secondary system. It was regularly in use until it started to intermittently lose one channel about 5 years ago, when it was replaced by a Quad 33/303 amp.

So I decided it was about time to get it on the bench, it certainly is a heavy old beast!

I blew away 36 years of dust, connected it up to my workshop speakers and CD player and powered up. I was greeted by music from the left channel only, the balance control was very scratchy so this was given a dose of Servisol, along with the tone controls and this sorted that problem. Wiggling the tape monitor switch bought back operation of the right channel, but the only way to get some Servisol into it was via the front of the switch with the amp tilted upwards.

With the amp now working as it should, I left it playing while I went in for a cuppa. On my return the right channel had gone off again

After some closer inspection, the problem turned out to be some dry joints on the preamp board beneath the muting switch!

I left the amp on all evening with no further problems, so it was given a good clean externally. I then decided to try it out in place of the Quad.

Wow what a revelation!
Connected to my Marantz CD73 and my Tannoy 638's and it blew the Quad into the weeds. The sound quality is simply stunning, far better than I remember, so it is now back in its rightful place.

Amps like these should be cherished, you would have to pay a fortune to match both its build and sound quality.

As can be seen in the photos it has four output trannies on a massive heatsink for each channel, two massive caps and huge transformer.

They just don't make them like this anymore!

Mark
Attached Thumbnails
Click image for larger version

Name:	amp1.jpg
Views:	3573
Size:	90.6 KB
ID:	65582   Click image for larger version

Name:	amp2.jpg
Views:	8242
Size:	121.6 KB
ID:	65583   Click image for larger version

Name:	amp3.jpg
Views:	2987
Size:	135.9 KB
ID:	65584   Click image for larger version

Name:	amp4.jpg
Views:	5243
Size:	136.1 KB
ID:	65585   Click image for larger version

Name:	amp5.jpg
Views:	11113
Size:	136.1 KB
ID:	65586  

mark pirate is offline