Description
NIKKO GAMMA 1 FM TUNER This tuner works absolutely works great. It attracts distant stations. It sounds beautiful.All of the lamps including the stereo beacon WORK.This is a massive 12.5#, well built, well designed tuner. From FM tuner info:Nikko Gamma I (1977, $400, black w/matching amp, silver, service manual, schematic, Audio review) search eBay The Gamma I is a 5-gang, FM-only, rack-mount style analog tuner that was sold in black and silver. It uses one LC filter and one SAW (surface acoustic wave) filter in the wide IF bandwidth mode, and 4 standard 3-pin ceramic filters in narrow mode, and has what some feel is a particularly effective high-blend circuit. Our panelist Bob says, The Gamma I has been praised by two people I trust. It uses the HA11223W MPX chip, same as the Gamma V. Looks tough to mod, with one board above the other, but not impossible. Looks to be discrete outputs also. Our contributor Hank adds that the Gamma I has a fundamentally sound design. I have not yet had mine modified but it has been restored (all marginal or suspicious parts replaced) and aligned. It is a very nice tuner and I suspect that it has significant potential for improvement.Our panelist JohnC did indeed improve his Gamma I, twice no less! Heres Johns initial report: These units sound pretty good as is, but they do respond well to simple mods. I did these without benefit of a schematic. The power supply is easy to get to just by removing the covers, so that got recapped. Bob said looks to be discrete outputs also, which I read to mean discrete components, but there are definitely op-amps in there. To be specific, TA7136P ICs are used, the same as what are in the Sansui TU-9900. I did manage to identify the input and output caps to the op-amps and changed those out, but without a schematic Ive stopped there for now. The IF strip is located on its own board located above the main board and prevents full access without removing it, not a simple task bet definitely doable. What was interesting was that this unit did not have the SAW filter installed in Wide mode. The LC was there but the SAW was replaced with a 3-legged ceramic Murata, tan body, yellow dot, marked E10.7A with the Murata logo and a stylized X on the next line. This appears to be a factory change because I can see no indications that the SAW was ever installed. Anybody else ever see this? Bottom line is that after a little tweaking these units sound real nice, reasonably selective and sensitive, at least in my market.But wait, theres more! John got hold of a service manual (now linked above) and went back inside. The tuner has a 5-gang analog front end employing two MOSFETs which feed dedicated Wide/Narrow IF strips. The narrow strip employs 4 ceramic filters, blue body/red left color dot MM-A series, the Wide an LC filter and a SAW. I received this one with the SAW replaced with what I believe is a 175 kHz, tan body/yellow center dot CF with no other circuit changes noted. The IF feeds an HA11211 FM/AM system IC with only the FM side used. It feeds a TA7061AP IC and then into a ratio detector. The HA11211 does contain a quadrature detector but it is not used. The MPX IC is the venerable HA11223 out to TA7136P op-amps. There are both fixed and variable outputs, with the variables running through about 28 inches of wire. The fixed RCAs are tied directly to board trace and are close to the op-amps. The power supply provides balanced 13V and single-sided 12V rails. The audio TA7136 op-amps are operated in balanced mode, while all other ICs are run single-sided.
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