JVC JA-S44, a restore, and some respect for good design.

[Reelly]

Thanks ElectTech for the manual referral.
However, after a lot of squinting at the dodgy scanned schematic I had, managed to fix the relay problem.....a dead diode.

If I was keeping the unit, I would probably invest in the service manual (wish somebody would put it on Hifiengine.com, as there are quite a few people after it) and "attempt" the excellent restoration you did on yours. However, prefer my JVC JA S77 and JVC SEA 70 combo, so will be moving it on.

Cheers

 

[Wire Nut]

Hi, does anyone know the voltage of the lamp/fuse for the VU meters? The only ones I can find for sale are from Eur-Asia and take a month to get to the US. The service manual does not seem to mention them,
Thanks... Nut

 

[Wire Nut]

It is 12v. I am almost done with my recap/ upgrade and will post some photos soon. One more thing, I have the US model and there are a LOT of caps that are not on the service manual so be sure to take care of replacing them one pair at a time!

 

[Wire Nut]

If you are thinking about getting one of these and refreshing it, ignore ElectTech as it sounds great if you use quality components. One of my Marantz Model 5's conked out and I am using my upgraded 44 in my main system now, it sounds great! I very much like the fact that you can EQ your sound to fit the room acoustics. I used mostly Panisonic caps except for critical areas. I used Nichicon for the filter caps which I bypassed with K42 PIO caps, I will post pix soon.

 

[Wire Nut]

On my unit I used some WIMA on the tone board and Panasonic for the other electrolytes except the filter caps which are Nichicon Gold Tone. I damped the chassis and the lid (photo of the lid included). I took out the thick tinned wire they used in the phono section and installed Cardas shielded cable, I also installed some nice 5 way binding posts to accommodate my 9 AWG speaker cables. I took out the Litz small gauge power wire and replaced it with 17ga AntiCable solid core wire which I twisted. To make it look a little less plain Jane I painted the volume and EQ knobs black. Since the original paint is metalized I use etching primer first. I installed blue LED's but didn't like the color... I have samples of over 150 stage light films and found a nice light turquoise to get a color that I liked. You can see my lonely Model 5 below the cabinet, the amp is at the doctor... it is a special tech that does tubes and has all of the old style caps and resistors to keep it in the original state. To repeat, this amp sounds pretty darn good, I used caps on hand but if I were buying them now I would say I only have around $300 or so into it so it s really a good value.

 

[ElectTech]

@Wire Nut

I am revisiting this old thread about the JA-S44. I had to replace a noisy opamp (HA1457) sometime ago. So, for those interested, a solution is to use an ‘HA1457 Upgrade Adapter’ from www.cimarrontechnology.com

I replaced the old HA1457 with an OPA134. However, you must reduce the voltage to the opamp from +/- 20.8V to below +/- 18V; otherwise, the new opamp will be damaged. A solution is to replace R217 and R218, each with two 4.7V Zener diodes in series (1W each). So, the voltage from the +/- 25.4V power supply is reduced to +/- (25.4 - 9.4) = +/- 16.0V.

The +/- 25.4 V power supply voltage shouldn’t be changed because it also feeds the phono stage with this same voltage. (In fact, I removed the entire +/- 25.4V power supply from the PCB and built one external using LM337 and LM338 voltage regulators – I did this to remove the factory brown glue from the PCB, and to keep the heat away from the VU meters, whose lamps are now 12V LEDs)

The equalization stage uses the same voltage of the opamps, i.e., now +/- 16.0V. I fully tested it, and the equalization stage also works fine with +/- 16.0V.
I hope it can help other folks who own a JA-S44 and need/want to do this opamp upgrade.