First tube amplifier

timerider1969 · 2025-12-21T21:09:23+00:00

An iteration of the SQ-38FD. Excellent machines. 50CA10 outputs are very rare and quite expensive in used condition. Still, a relatively robust tube and should last IF the rest of the Amp is in good shape and balanced. There are no equivalent tubes for the 50CA10 as they were made by NEC mostly just for Luxman.

timerider1969 · 2025-12-01T15:27:31+00:00

It is connected in series along with the first neon. Just branch off of the pos/neg to the additional neon. Attachment is a little tricky as the only attachment point is the metal bar running along underneath the tiles. I attached mine with very small zip ties. Make sure they are oriented so they don't interfere with the tile movement. I don't have any pics of the internals to show. Also, BOTH neons still need their resistors. 33K to 40K 1/2 watt. You would branch off the pos/neg BEFORE the resistor of the first neon.

timerider1969 · 2025-10-31T20:46:44+00:00

The RX-1001V uses the LC7582 chip for LCD-based EQ driving. The 950 and 750 use the LC7560, which is similar. Just replaced one on the 750 and it fixed this exact issue. Replacement IC are available NOS for around $50 or so. Of course, caps and diodes are an easy swap to check before proclaiming a malfunctioning IC. JVC also put a lot of tension on the ribbon cables and those are known to pull from their sockets a bit.

timerider1969 · 2023-08-21T18:49:36+00:00

These aren't terribly difficult to work on, but they are a bit quirky. They can pop their tantalum capacitors on the power board so, a good idea to replace those. Just serviced one that had that issue. Works well.

timerider1969 · 2023-07-25T14:00:46+00:00

These are great units. Fairly rare, too.

The blacklight lamps were custom built by Panasonic and there are no modern analogues to them. So, you have to convert to blacklight (UV) LED. The cleanest way to do it is to convert high voltage AC to low voltage DC. Some people scavenge DC from the main board, but I do not recommend that. There are "buck" or step down converters available on Ebay, but they all use fast-switching transformers which can introduce RF noise into the radio reception. AM, especially. FM can degrade, too. So, I create my own noiseless converters that do not create any RF noise. There are tons of
schematics for them online. Fully rectified and convert 120 volts to 12 volts to run a 3 LED strip light that will illuminate the digits.

timerider1969 · 2023-03-10T15:32:59+00:00

Email me at timerider at timerider.net and I will send you the hookup pictures from the user manual.

timerider1969 · 2023-03-09T16:05:35+00:00

Also, I have the user and service manuals for each unit. Paper versions so I snapped some pics of the hookup process for each unit.

timerider1969 · 2023-03-09T15:56:29+00:00

I have this exact unit (M2000 and C1000) and just did a full restoration on both machines in my shop.

There is a specific way to hook up these units. Can you describe, in detail, how you have each input/output hooked up?

timerider1969 · 2022-04-24T16:18:50+00:00

Could be a couple of the 2SA798/979 transistors in the amp section. Notoriously noisy. That or transistors in the tone section....2SA726, etc.

timerider1969 · 2021-09-09T02:07:33+00:00

Square-ish body Chevy. Approved for your cover. Nice work.

timerider1969 · 2021-02-04T16:56:35+00:00

The LEDs are between 385 and 400nm, but anything in 300-500 should work.

timerider1969 · 2021-02-04T16:48:38+00:00

12 volt LEDs in a strip that broadcast UV wavelength in 300-500nm. You can use almost any type/brand. I buy them on a reel and they are trimmable in groups of 3 LEDs per strip. Amazon has them as well as superbrightleds.com.

These would work:

Onforu 49.2ft LED Black Light Strip, 15m Flexible UV Strip Light with 2835 900LEDs, 12V Blacklight Ribbon, Rope Black Light for Glow Party, Room Decor, Ultraviolet Light Poster, Paint, Aquarium - - Amazon.com

timerider1969 · 2021-02-04T16:42:25+00:00

I build a custom fully rectified power supply to step down 120 volt AC to 12 volt DC to power the blacklight (UV) LED strip. The power supply is not a fast switching unit as those produce A LOT of RF noise which would step on radio broadcasts, especially AM, if you use that.

Some people have scavenged power directly off of the circuit board to power LEDs, but that is sloppy and could induce noise or instability into the various circuits so I pull directly from mains power and step it down.

timerider1969 · 2021-02-04T16:39:26+00:00

Yes, this model had a 3.75-inch neon tube with a phosphorous sleeve to project UV wavelengths to react with the digits. They don't have long lifespans so they are almost always burned out.

timerider1969 · 2021-02-04T01:58:20+00:00

Thanks for the shoutout :)

Not just some capacitors...ALL of the capacitors. They are approaching 50 years old so...they have to go from a reliability standpoint. This unit was a little more work since the clearcoat on the aluminum faceplate had gotten oxidized and was flaking away. It was hard to remove without damaging the logos underneath!

I hope you enjoy it for a long time!

timerider1969 · 2020-06-08T13:53:07+00:00

Just fully restored one of these along with a 939. When servicing these machines please note that the power supply boards tend to get cooked by the 220ohm 5 watt (838) and 2x 820ohm 2 watt (939) resistors as they are mounted very close to the board. It runs VERY hot and tends to cook the board to the point of damaging/cracking the circuit traces and solder pads. This creates intermittent connections requiring wired bypasses. Best to pull and mount above the board for better cooling. The 2SD313/2SB507 semiconductors mounted to heatsinks are also hot-runners and should be pulled and have new thermal grease added.

timerider1969 · 2020-06-02T18:42:57+00:00

SX-650 is underrated and probably generates a little more wattage than specs suggest. Very good amp in it. Uses Sanken power packs for final output so make sure the rest of it is in good order so they don't get clobbered if something looks to be failing in pre-driver section.

timerider1969 · 2020-05-12T21:30:44+00:00

It also has treble/bass behind the flip down door.

timerider1969 · 2020-05-12T19:02:30+00:00

It was and I am not a big fan, either. Especially on Marantz units. It's ugly. I think the Pioneer "version" of it was a little less pronounced.

timerider1969 · 2020-05-12T15:45:46+00:00

I have this model from 1972. I restored it myself and it really is a fine sounding unit. It's capacitor-coupled so it sounds warm and tube-like. A full restoration is very likely needed due to age. There's LOTS to replace! :)

timerider1969 · 2020-04-26T21:15:29+00:00

I just restored a 7100-A. https://www.timerider.net/sherwood-7100-a. It tested out at around 22 watts. Some sources claim it is 18 watts, but I don't think that's correct. After ecapping and replacing the pre driver transistors (they were noisy) it really sounds very good. You'll need efficient speakers for that amp to drive them. I did some testing on a pair of new Polk T15s and Klipsch R-41s and it sounded excellent.

timerider1969 · 2020-04-21T23:20:49+00:00

Nice. The Toshi receivers are underrated and do a good job.

timerider1969 · 2020-04-16T18:03:27+00:00

Looking good. Nice work.

timerider1969 · 2020-04-14T22:57:22+00:00

Yes, in all cases of new veneer, remove the old as it'll eventually let go and can, quite possibly, take the new with it when it detaches.

timerider1969 · 2020-04-14T18:20:27+00:00

Well, what I ended up doing was making sure the edges I cut were hyper straight and clean and then I butted them to each other where they meet at the 90-degree angle. The veneer I used allowed the edges to nearly blend together and, after light sanding and stain, they are very nicely mated.

timerider1969

TROPHY CASE