A poor man’s Marantz: adjusting a Superscope R-1270

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In 1964, American electronics company Superscope bought Marantz from its founder, Saul Marantz. Superscope owned Marantz through the 70s, and it had two product lines: quality line under Marantz brand and budget line under Superscope brand. Both included the whole range of hi-fi products (amplifiers, tuners, receivers, turntables, tape decks and speakers), and both were designed by Marantz engineers. While they shared design ideas, Superscope brand products were built to a less strict specs and with cheaper (but still good) components, some of them also in cheaper location – Taiwan, while most Marantz products were made in Japan. In short, Superscope was a poor man’s Marantz. The differences faded towards the end of Marantz’s ownership by Superscope and in the late 70s the products from both lines had mostly cosmetic differences, for example Superscope A-530 was Marantz Model 1050 with a plastic front and microphone input instead of two pairs of speaker binding posts, but otherwise exactly the same down to the cheap cardboard bottom plate.

While originally Superscope products were not as good as their Marantz counterparts, ageing components leveled the playing field and right now unrestored Superscope and Marantz amps and receivers offer similar quality. Unfortunately, flippers caught wind of the pedigree and Superscopes are not dirt cheap anymore. They are still usually a bit cheaper than vintage Marantz though.

Another difference is availability of materials. Specs, user and service manuals for any Marantz product from the 70s are very easy to find. With Superscope it’s difficult to impossible. So, if you have a Superscope that needs servicing or adjustments, you have to get creative.

I bought a Superscope R-1270 5 years ago and liked it so much that I decided to keep it in my collection. With black face, normal tuning knob instead of a gyro wheel and thick veneered board top and sides it does not exactly scream “Marantz”, but the style of tuning dial, signal meter, indicators, push buttons, balance slider in the middle and the entire rear panel are dead giveaways. More under the hood: it has Marantz boards, Marantz output transistors, the same fuse-type lamps and so on. It is a Marantz, no doubt. Superscope R-1270 is a 35 WPC Superscope receiver, top of the line that also included models R-1240 and R-1220. It was also sold as Expert TA-960. According to some sources the amp section is based on Marantz Model 1070 amp, but I think it’s actually based on Marantz Model 2235 receiver: both are quite similar, but R-1270 has the same outputs as 2235, and 1070 has different outputs. The preamp, phono stage and tuner section are more modest, they appear to be “borrowed” from Marantz 2215B. My unit needed a new volume pot, other than that it worked fine. I used it for a while and then moved on to the next toy, and the Superscope ended up on a shelf.

I do take it out every few months to clean it and run it for a few days, make sure it stays healthy. Last time I did that I remembered that I’ve never tried adjusting the amp, so I figured I’d try adjusting DC offset and idling current. Of course service manual for R-1270 is not available (for free anyway), so I tried to figure things out based on manuals for 2235 and 1070. I was working on an assumption that Marantz engineers would not make any major changes to the circuits between two very similar amplifier boards with the same output transistors, so that the adjustment procedures should be similar or the same for Superscope R-1270 and Marantz 2235.

Here’s the amp board and outputs of Superscope R-1270:





Here’s the adjustment procedure and amp board layout for Marantz 2235:


Z2235 procedure

Figuring out DC offset was very easy. There are 4 trimming pots on top of the amp board, the inner pots adjust DC offset (like in Marantz 1070 and 2235). DC offset was quite healthy (fluctuating within 5mV for each channel), but I still adjusted it to 0.1 mV, because why not.

Idling current was a bit more tricky.

The outer trimming pots on top of the amp board adjust idling current, again like in Marantz 1070 and 2235. According to service manuals for those two, the procedure for adjusting idling current is to connect a DVM to two pins at the bottom of the amp board. These pins (measurement points) can’t be accessed without dismantling the amp board.
But I figured out that I didn’t have to bother with the not-so-accessible pins at the bottom of the amp board, because it’s the same as measuring across the emitter resistors, and those are a bit easier to access (no need to dismantle anything when measuring across single resistor). Using the board from 2235 as an example, adjusting across pins J713 and J717 would be the same as adjusting across resistors R756 and R758 to 8 mV, or across one of them to 4 mV.

That’s what I did and nothing exploded.

But then I noticed that the value of these resistors is different in my R-1270 than in Marantz 2235/1070. In Marantz 2235 (and Marantz 1070) resistors R756 and R758 are 0.22 ohm, their counterparts in R-1270 are 0.5 ohm. So the question was, how should I change the value of the idling current measured across these resistors? The answer is simple: double the value of resistors, double the voltage across them. So, if idling current in Marantz 2235 is 8 mV across two 0.22 ohm resistors (4 mV across one), it would be the same as around 16 mV across two 0.5 ohm resistors, or 8 mV across one resistor.
At first I adjusted with a small safety margin, to 6 mV across one emitter resistor. After consulting and confirming that my reasoning was correct I readjusted to 9 mV across one emitter resistor. As a general rule, the idling current for a class AB amplifier should be 10-30mA. As expected, the value for Marantz 2235 is within this range at ~18mA; similarly for Superscope R-1270, the reading across both emitter resistors can be ~18mV (for an idling current of ~18mA).

Idling current should definitely be checked in these receivers (and Marantz amps and receivers with similar amp board design). In my Superscope R-1270 before adjustment it was 30-40 mV measured across one emitter resistor, which is 3-4 times higher then the recommended value. This may cause undue strain and excessive heating of output transistors, ultimately leading to their premature demise.

About the sound: Superscope R-1270 sounds a bit darker than Marantz amps receivers from the same period, so it’s a better match with brighter, sharp sounding speakers. It was right at home with Quadrals with titanium dome tweeters and with older Celestions. I would not match it with the likes of Tannoy M2 or Wharfedales from the recent Diamond line. It is very generous, maybe a bit too generous with bass, but seems to lose some detail in LF. In general, it is a very pleasant sounding receiver, if not very detailed. Functionally, it is similar to lower Marantz models: 3 line inputs including 1 tape loop, a decent phono stage, unfortunately no main in/pre out jacks, so you can’t use it as a preamp. One function that Marantz stereo receivers from the 70s usually do not have (but some amps do, like the 1070) is Quadraphase, which is a simulated quadraphonic effect obtained by changing phase of the rear speakers. While not a match for a proper quad, It does sound good with some recordings. Like most receivers from the 70s, Superscope handles 4 Ohm speakers without any issues.

Superscope R-1270 is very capable receiver, and definitely recommended. It does not sound or look exactly like a Marantz, its dark face matches the sound, but it shares many qualities with its Marantz family: pleasant, smooth, warm and powerful sound and good built quality. If black is your color, it is also one of the few receivers from the 70s that are black and make black look really good.


Technical information:

Designed by Marantz USA
Made in Taiwan, China
Years: from 1976


Output power (RMS, 8 Ohms): 2×35 W
Total harmonic distortion (THD): <1%
Intermodulation distortion (IM): <1%
Channel separation: 56 dB at 1 kHz
Frequency response: 15-70000 Hz, -3 dB
Power bandwidth: 40-20000 Hz
Damping factor: >44
Dynamic range: 100 dB
Input sensitivity: 2.8 mV/47 kOhm (PHONO), 180 mV/100 kOhm (TAPE, AUX)
Output (Speakers): 4 Ohms or higher


FM: 88 – 108 MHz
AM: 525 – 1605 kHz
Sensitivity (FM): 1.9 uV
S/N (FM): 60 dB (stereo), 78 dB (mono)
THD (FM): 0.4 % (stereo), 0.2% (mono)
Frequency response (FM): 30-15000 Hz
Stereo separation (FM): 46 dB


Power consumption: 26 W (idling)/160 W (rated power output)/220 W (max. power)
Dimensions (WHD): 43 x 12 x 29 cm
Weight: 9.6 kg


  1. Chris

    You’re right about the relationship between Superscope and Marantz. Those were Marantz output sections. You should try to use 0.22 ohm resistors in your 1270 and set the bias to compensate. That will probably then sound exactly like a Marantz 2235.

    The Superscope receivers I have repaired all had silver faceplates, never seen a black one. Could be the difference between Canadian and US models I guess. They were good sets though, no doubt. It’s too bad that most receivers are being damaged by the hoard of flippers who “recap” receivers. That and the prices are just stupid these days. What people need to do is find a good audio technician who used to work on Marantz receivers and have it properly restored. It would be nice to see them saved from the hackers iron!

  2. rafal lisinski Post author

    Well, I just set a higher bias (mV) to account for .5 ohm resistors, the end result should be the same as using .22 ohm resistors and setting a lower bias, right?

    The black face is gorgeous on this one. I used to have a Marantz 2226 in black as well, that one looked good too (but the Superscope loos better IMO). Now I’m trying to score an older “princess pink” Superscope receiver, but unfortunately flippers have caught on and the prices have gone up on those. I do have a Supersope A-260 amp, it has some pink lights too.

    Luckily most people around here have the “if it ain’t broke, don’t fix it” approach, so most classic Marantzes I see have original parts. But I agree that finding a decent technician for anything is not easy these days, let alone Marantz. I should know, both my quad Marantz receivers (4240 and 4400) needed some repairs.

    1. Charly

      Tengo un r1270 está óptimo pero honestamente no se como conectarle las bocinas ya que no tengo las originales, solo cuento con 1 par de 16 omhs, 1 par de 8 omhs y 1 par de 12 omhs (los Subwofer). Ya que trae 2 salidas de principal speakers, 2 salidas de remote. Aparte abajo trae salidas de quadraphase…. Ayuda xfavor

      1. rafal lisinski Post author

        You connect one pair of speakers to MAIN.

        You connect the other pair of speakers to REMOTE – then they play exactly the same sound as the MAIN speakers.

        Or you connect the other pair of speakers to QUADRAPHASE – then they play a bit altered sound to create fake surround effect.

        You don’t connect the subwoofer at all, unless you can connect the MAIN speakers through your subwoofer (it is possible with some subwoofers).

        Conecta un par de bocinas a MAIN.

        Conecta el otro par de bocinas a REMOTE; luego, reproducirán exactamente el mismo sonido que los bocinas PRINCIPALES (MAIN).

        O conecta el otro par de bocinas a QUADRAPHASE, luego reproducen un sonido ligeramente alterado para crear un efecto quasi-surround.

        No conecta el subwoofer en absoluto, a menos que pueda conectar los bocinas PRINCIPALES (MAIN) a través de su subwoofer (es posible con algunos subwoofers).

  3. Wade

    Was wondering if you could tell me the value of the cap that’s on the back of the tuning meter. My friend’s R1220 isn’t working. Think the cap may be bad. Thanks.

    1. rafal lisinski Post author

      Unfortunately I can’t look at my Superscope R-1270 at the moment. But this cap should be the same as in corresponding Marantz designs, and that is: 100uF 10V electrolytic cap.

  4. Gary

    New to researching, purchasing Audio. I just took early retirement and have enjoyed searching, finding and buying such treasures.

    I bought a SuperScope today at a sale for $20. A light is out, maybe 2, on the left side when looking at tge faceplate.

    I hooked it up to the closest speakers sitting idle and it sounds surprisingly good. Listening to Steely Dan at the moment through old Pioneers.

    The seller was awrsome, gave me an old Sherwood Tuner, l believe made in Chicago.

    If anyone knows the Specs on the R-340 Receiver l sure would appreciate any help..

    Also purchased a Marantz 2226e, and havent fpund any info on the “e” model.

    Tuner works good

    1. rafal lisinski Post author

      Gary, congratulations on your purchase! Superscope R-340 is a cute receiver, on my “to get” list (pink lights!). And $20 is a great price for a decent vintage receiver that works, even a low power one like the R-340.

      Superscope R340 is from 1973, it is rated 10W per channel at 8 ohms (RMS), its peak (music) power is 15W per channel. You’ll find other specs in the file I emailed you. BTW, 10 WPC is more than enough for listening at home, unless you have a really big room or like to listen very loud. But better avoid boosting bass or using loudness at higher volume levels.

      For dial and meter lights you will need 8V 250mA fuse lamps (the same ones as in Marantz receivers). My advice is to use regular lamps (not LEDs – my personal preference, regular lamps look better to me) and to replace all lamps, not just the ones that are out. You can keep the old ones that work as spares. Stereo light is probably a 8V (less likely 6.3V) 40mA bi pin lamp. DO NOT USE a stronger lamp (for example 60mA) – it could damage the tuner. If that lamp works, best leave it alone.

      Marantz 2226e is simply a European version of 2226. The same specs apply and the service manual is the same. The only differences are that the “e” has mains voltage selector on the rear panel and a low filter switch on the front panel, the non-“e” (US model) does not have a voltage selector and instead of low filter it has a 25μS setting is for altering the FM de-emphasis. Low filter is more useful, especially if you have a turntable.

  5. Ron Langan

    My superscope 1240 has speaker “thump” or crack on powering on and off. Suspect the capacitors in the speaker line. Happens in mono & stereo.
    Advice needed on which caps specifically to replace.

    1. rafal lisinski Post author

      Speaker “thump” while turning on/off is normal with vintage amps and receivers, and newer ones that don’t have relays too for that matter, I have an Exposure amp that has quite a loud thump. Here;s a quote from its manual: “Our amplifiers exhibit turn-on and turn-off transients, heard as “pops” or “thumps” through the loudspeakers. These transients can cause no damage to the loudspeakers, are indicative of normal operation, and such are no cause for alarm.”

      As far as the cracking sound goes, power switch would be my first suspect.

  6. Doktor

    I have a service manual for the Superscope R-1250. It says to measure for dc offset and adjust R761 and R762 for 0 volts. Then it says put a scope of the speaker outputs. At 0.5 Watt adjust R763 and R764 for no crossover distortion. It then says Caution avoid excessive bias current. (20mA ~ 30 mA at no signal)

    1. rafal lisinski Post author

      The amp section in Superscope R-1250 is different, it’s a 25W per channel amp, so the procedure is similar, but not the same. Another problem is, not many people have a scope at home. In most cases, people have to adjust without a scope, which means adjusting to mA or mV values.

  7. Paul


    I have the R-1280 model. It seems quite rare. I can not information on it anywhere.. It keeps blowing 2 of the fuses. I cant even find a schematic for it anywhere.

    Very good rightup on the 1270

    1. rafal lisinski Post author

      Unfortunately I don’t have a schematic for the R-1280. But on the outside it is nearly identical (different finish, but exactly the same functions, layout of buttons and sockets etc.) to the R-1270. Look at the photos of the R-1270 and compare to what you see under the hood of your R-1280. Compare the boards, output transistors etc. Maybe it’s the same receiver with updated looks, or at least similar enough to use the R-1270 schematic to repair your R-1280.
      If it is identical or very similar inside, do let me know and send me a few pics, I will add this info to my article.

  8. paul malloy


    I have a Superscope R-1240 in really good condition. Doesn’t look like anyone has ever been inside it.

    It did come with several issues. Dead signal meter and of course burnt out lights.

    Big issue is the volume pot. Left channel still is has volume when pot is at zero (Right channel has no sound at zero). I figure that the wiper is off a bit on the shaft and maybe able to be fixed. But, if not, can you tell me what volume pot you used on your R-1270? Did you find a Superscope one or did you use a Marantz one. The part number for the R-1240 is RM0254023 (according to the manual) and RM02540232 (according to the part number on the pot itself) – 250K X2. Not sure if the R-1270 and R-1240.


    1. rafal lisinski Post author

      Hi Paul, I had exactly the same problem with the volume pot in my Superscope (channel imbalance at low volume, one channel had sound at zero volume). If I remember correctly, I used a generic volume pot obtained locally. As long as the pot physically fits, has the right taps and the right specs, it will be fine. Dead meter – I’d start with checking the electrolytic cap on the meter, it might be the culprit.

        1. Brent

          Hi Rafal and Paul – found this as I am also working on a Superscope R-1240…it had a blown transistor, which I have replaced and it seems to be working very well. Planning on doing a full recap also. Luckily my volume and other pots seem ok so far…

          Paul – I was wondering how it is going on yours? My meter (and the light for it) is also not working. I changed the capacitor and no change. Just wanted to check if you found the problem before I get into it?

          Also wondering if either of you have any idea on the bias setting?


          1. rafal lisinski Post author

            I haven’t found the R-1240 SM for free anywhere. Your best bet is to do what I did – find a Marantz receiver from which this Superscope’s amp is copied and use the bias adjustment procedure from the Marantz SM, accounting for possible different resistor values (like the 1270 had). I would start with comparing the amp section in your Superscope R-1240 to Marantz 2220.

            Unless you’re willing to buy the SM, then it’s apparently available here: https://www.vintageaudiostore.com/products/superscope-r-1240-receiver-service-manual-original
            But: I’ve actually found the SM for R-1270 some time after writing this article and the procedure for bias adjustment is useless for me (it requires an oscilloscope, which I do not have). It’s quite likely that it will be the same for R-1240.

        2. Ernie Coombes

          I have the R-1240 “Service Data” manual and can confirm the DC bias/offset is adjusted by the inner pots (R761 & R762) on the P700 main amp block (the one connected to the heatsink). With selector switch in the “AUX” position, Adjust R761, R762 for “zero” DC output (at the speaker outputs)

          Idling Current is adjusted using AF oscillator connected to the AUX jack | 1000 Hz | connect oscilloscope to speaker terminals | adjust R763, R764 (outter pots) for no evidence of crossover distortion at 500 mW output.

          CAUTION: Avoid excessive bias current
          (20 mA ~30 mA at no signal).

          1. rafal lisinski Post author

            Thank you, that will be very helpful for all the R-1240 owners out there!

            I’ll just add for anyone who does not have an oscillator and wants to adjust to a safe value: 20 mA at no signal should do the trick, for mV value adjusted across output resistors – calculate based on the value of resistors.

  9. james

    Great article, i too have a R1270, silver face. Nice sound, a little warmer than the Marantz 1070 sitting next to it. Have re-lamped with LEDs and it looks pretty. Pops on power off were fixed with a service / recap in the amp stage. Have noticed that at minimum volume there is still sound from source, do all of these behave that way or is there adjustment that is out?

    1. rafal lisinski Post author

      James, yes it is a common behaviour in this model and it’s not a matter of adjustment. It’s a faulty (or poor quality) volume potentiometer. My R-1270 had this problem, as did at least two more units that I know of. With a new volume pot, the symptom disappeared.

      It’s not a big problem and I haven’t heard of it getting worse over time. I replaced the pot in my R-1270 mainly because in addition to this symptom it also had channel imbalance that required compensating with balance pot during quiet listening.

    1. rafal lisinski Post author

      No. They are similar but not identical and many parts are different, starting with output transistors. Service manuals for both receivers are available (for free) on hifiengine, you can download and compare them for more details.

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