Restoring a 57 Year old Receiver: The Pioneer SX-1000TA from 1966

I usually write about new designs, technical aspects of audio etc but on one previous occasion waxed lyrical about the JBL SA600, a vintage stereo amplifier from 1966 designed by Bart Locanthi, which has turned out to be one of the most popular pages on hifisonix.com – it regularly tops the monthly hits table.

I am going to share a few thoughts about restoring a vintage Pioneer SX-1000TA stereo receiver. First, a bit of history. I’ve rooted around on the web and YouTube and from what I can tell, this is the original receiver that kicked off the Japanese audio invasion starting in 1967/8. This cemented their dominance in the home audio field for the next 20 years until the late 1980s, when widespread interest in home audio seemed to wane, probably due to multiple factors like the arrival of the Sony Walkman in July 1979 and its progeny, portable CD and MD players, but also the rise of computer gaming. ‘Personal audio’ epitomised by the Walkman seemed to shift the appreciation of music up to the 1980s from being a family activity in a living room to something individuals with headphones did while on the move. Besides, it was a good way to block out the din and hubbub of city commuter life. In January 2001, iTunes was released followed in October that year by the Apple iPod, basically finishing off the home audio components industry as we know it. Homes up and down the country no longer seemed to want those beautiful Japanese receivers of yesteryear with their fantastic blue and green tuning dials, VU meters and plethora of knobs covering tone controls and filters, tape dubbing facilities and speaker switching. Fast forward 30 or 40 years to 2025 and vintage receivers from that era are objects of desire.

The ‘aesthetics’ war raged for about fifteen years, with two examples shown above, until manufacturers drifted towards ugly black boxes, which in my purely subjective opinion, also helped finish off the segment.

Pioneer Corporation opened its first US sales office in 1966, but was in effect waiting for a hit product to really grab consumer attention, and that product came long in the form of the SX-1000TA, but via an unusual route. Serviceman returning from Vietnam via Japan, or having taken active duty leave in Japan whilst out there, had picked up Japanese receivers, the SX-1000TA being one of the early examples, introducing many folks back home to Japanese products that were every bit as good as US brands like Fischer, HH Scott, Marantz and McIntosh but at a much lower price points. The SX-1000TA brought Pioneer the brand attention it needed to really take off with consumers. It looked cool, and at 40 Watts per channel produced loads of power for the day (most receivers and amplifiers were in the 20 to 40 watt range). It quickly established itself as a durable, well-built amplifier – the fact that these are still being restored and repaired nearly 60 years later attests to that. In the early 1970s, the ‘college audio revolution’ took off which saw dorm rooms and campus radio stations across the US sporting Japanese audio systems, with Pioneer featuring particularly strongly.

My particular unit, pictured below on my workbench, dates from 1966/7 as far as I can guess, and has a vacuum tube-based FM tuner. I went to a local garden shop (now defunct) in about July 2019 to buy a bag of compost and happened to wander around the back of the shop where I discovered a room full of ancient, decrepit looking audio gear and musical instruments. The SX-1000TA was lying on its side and I enquired about it and was told it was working and I could get it for £20, but not the £10 that I offered. I parted with £20 and soon discovered back home that it was barely working. One channel was completely dead, FM stereo didn’t work properly, and the side that did distorted terribly and the various pots and switches crackled and popped in use – some ‘Servisol’ switch cleaner seems to have resolved most of the problems, and the potentiometer crackle (now much reduced) is an indicator of cap leakage which is to be expected on something this ancient, and easily solvable with re-capping. The front panel was dirty (as of January 2025, I still have to tackle that) and the inside covered in some sort of fine sawdust, powder or similar that appears to have stuck to all the components. I presume this receiver sat on a shelf in a workshop or place of business somewhere for many years, getting turned on for 8-10 hours every day to provide background music. A miserable existence no doubt for something that started out really looking beautiful.

The first job was to get the amplifier working. The left channel had a blown TO-3 output device (2SC793 100V 7A NPN) so I replaced all 4 output devices on both channels with MJ15024 (250V 16A TO-3 NPN) since the 2SC793s were no longer available. Q901, the first stage amplifier was also gone in the faulty channel, so I replaced it in both channels with BC546 which I had to hand and that sorted the amp out. Using an old iPod as the source and headphones, the sound is rich and ‘mellifluous’ (I’ll come back to this later). After the initial flurry of activity, it sat under my workbench until late 2024, when I pulled it out to continue working on it.

Pictured below is an immaculate 57 year old SX1000TA dating from 1968 going for £599 in the UK on eBay.

The next thing that required attention was the FM tuner bit. It seemed to tune in very well, but the one channel distorted very badly and I could not get stereo out of it. I guessed the issue was around the MPX board and found that one of the germanium diodes (D701-D704 OA79s) was leaky, so replaced all 4 of these with OA91s that I got from Cricklewood Electronics who are based in London. I removed and checked C708 and C709 (1000pF film) which measured well, but given the passage of time were extremely flimsy and the leads corroded, so these were each replaced by 2 off 470pF NP0/COG in parallel. C710 and C711, both 10uF electrolytics that feed the output amplifier/buffer stage of the MPX unit looked pretty grotty, so I replaced these with 22uF bipolar 35V devices. After this, I checked the sound and the distortion was gone – FM sounded really good. I was unsure of the tubes in the FM tuner section, so as a precaution then ordered a new set from Langrex here in the UK for about £20 excl. VAT and shipping (6HA5 and 2 nuvistor devices 6CW4 – all of them NOS). I didn’t notice any marked change compared to the old ones but am happy to have taken the precaution of replacing them. Also, it doesn’t appear to have any FM alignment issues, which in my case is especially good as I do not have any gear to be able to do that. BTW, the user manual (there’s a link to it below) has the full AM and FM alignment procedure, so back in the day any radio tech would be able to repair the unit – and Pioneer weren’t the only ones that did this as almost every Japanese manufacturer provided a schematic, parts list and service related data in the back of the user manual. You just don’t have that kind of thing today – it really was a fantastic reflection in my view of a holistic approach to product marketing and after sales support and care. Nowadays, you are more likely to read stories about manufacturers (and especially high-end ones) refusing to provide owners or second-hand purchasers with schematics, as if whatever they did was that different or important that to reveal it to a repair tech would jeopardize the commercial viability of the company. Absolute nonsense of course.

As of January 2025, I still don’t have FM stereo reception, so there is more work to do. Once the FM stereo issue is resolved – I suspect it might have to do with the selector switch – I will take a look at the PSU. Despite the 40W RMS per channel into 8 ohms, the main supply consists of just 2 off 1000uF 100V chassis mount capacitors which do look like high quality items. I may upgrade these to more modern components at higher capacitance values, but will have to see if the bridge rectifier diodes (D901~D904) are up to the job.

Here are the schematics and detailed user manual. The schematics are beautifully drawn in my view and a work of art in themselves.

Here are some videos of repairs and/or restorations on this classic receiver from around the web.

To be continued . . .