Rebuilding Classic Hi-Fi amplifiers is okay for early 1980s low end market models as they respond well to strategic component upgrades, such projects have a low resale value on Ebay as they must be sold as 'Spares or Repairs', but this type of low initial value item is the one to use for a rebuild project.  It is important to know how to solder and how to protect circuit elements from heat and iron leakage current.   Plastic scale model kit-building helps develop the skills required for this rather difficult hobby.  Even the young electronic engineer ought to be discouraged from rebuilding Classics like the harman/kardon A 402 or Pioneer SA7500mkII, except to renew the old solder and only then in the knowledge that this is extremely laborious and difficult work, not recommended for novices.

See that transformer?  it's a real quality kind of power supply part 

See the smooth black mains transformer in the Technics SU-Z2, above left?  It's what we call a 'potted mains transformer!'  It's a transformer in a can filled with hot wax, allowed to dry solid helping reduce transformer mechanical noise, better yet, in small amplifiers like this, located near tuners cassette decks etc in stacking systems, it foils stray electromagnetic hum and ripple noise.  See other 'potted transformers' in tube gear like the good ol' harman/kardon Citation II from the late 1950s, but you can't mount a cassette deck on top of a twin powered harman/kardon Receiver!  -Too much hum from its two mains transformers!  Most reckon the boys at Technics always did a pretty fine job of sorting out their Solid State designs?

Components in high quality late 70s Japanese Hi-Fi amplifiers are unlikely to be improved in rebuilding, first run bad amplifiers in for 2 days constant using a CD player then after if the solder has been renewed.  The large Black Sleeve Elna smoothing capacitors may be unlikey improved with smaller brand new Elna, PHILIPS or BC components!  But...But...by the the time you get new Elna in there, your not going to want to swap them back, it's just too much hard work!  When reservoir caps need replacing the pilot light will dip with loud bass and volume out will be low, never mind too much the hum ripple in speakers as cables and design limits cause that!  Volume pots need sprayed with a switch cleaner to remove crackle although this crackle is more often the solder needing replaced!  Knobs and switches are rotated back and forth after spraying with de-oxit or superlube and worked WITH THE POWER OFF while the cleaner is wet.  Heavy smoker equipment is best to be completely avoided or sold as such for 'Spares & Repairs.'  Many Ebay sellers do de-oxit and superlube before sales.

Some of the most often changed components in amplifier rebuilds are the solder, resistors, capacitors, speaker output connections, hook-up wire and small or poor quality heatsinks.  A fashion has begun by novices in replacing components with absolutely no radio experience and this well-intentioned practice is not to be adopted.  Some engineers change the semi-conductors and power-supplies but this is not within the Classic approach.  Parts replaced in novice rebuilds are only basic elements having improved over the years.  These include the carbon film resistor, only some ceramic but all paper foil capacitors, some electrolytic capacitors, degraded solder, some hook-up wire, particulary signal carrying ribbon or basic wires and any fuse holders crumbling away or heavily oxidised.

SEE REALISTIC TM-1001 Tuner with Auto Magic tuning!

Right above  Note the plastic insert in all STA-2000 knobs not only those of concentric type - Radioshack threw their hat in, no effort was spared to show attention to every detail had been covered. The old analogue tuners suit a rebuild, as there will soon be a 'Switch Off' for these radio transmissions.  It's one reason why nobody need pay real high prices for tuners or receivers of the old analogue style.  They do offer a good source for Cassette Recorders fitted with an MPX filter, since old stereo tuners rarely have a high frequency above 15KHz.  Great claims made by Ebay sellers that a Nak Cassette Deck, does 20Hz-20KHz on a Normal tape, is usually at a very low recording level and enquiries ought to be made for the frequency response at +6dB!  Frequency Response advertised at -20dB and 0dB is not much use while at the useful record level of +6dB doesn't sell Cassette Decks!  

Look out for the REALISTIC STA-240 version of this Sansui T 80! 

Some people rate the Sansui T-80 above right extremely highly as a rebuild but comparing the stock T-80 tuner with a stock REALISTIC STA-2000 above right, proves why owners say they 'love their STA-2000'.  -If you want an analog tuner to enjoy the last days of the format - hear a STA-2000 or rebuild one!  The T80 in 1980, features the digital readout out the new style tuners and retains the knob as did a QUAD FM4 -as the knob is easier to adjust than the buttons adopted by so many.  The REALISTIC STA-240 has the dial and digital readout of the T80, note its knob style - rumor has it Sansui made the SA-2001 & 1001B amplifiers for the TM1001 tuner!  Plus Auto Magic is said to be electronically similar to Sansui Quartz lock!  A dial scale is an anathema to many fashion led buyers but in adjusting remember the number of turns on the parts affect the tension necessary for operation.  The T80 assures customers the two tuning formats are alike, increased noise also comes from the digital readout with the need for additional filtering but today with RDS that is just an essential part of listening even to the too large SONY ES tuners - with some of these a receiver is compact!  The idea that a dial scale analogue tuner sounds 'better' than a digital readout set is arguable.  Like CD players and cassette decks, the sound quality of trying different models may surprise you!  The sets ought to be run for a number of months before considering rebuilding as many left standing only recover with use.

A good project for the novice to gain some rebuild experience are small units like the Technics SU-Z2 mkII shown above, it doesn't have many supporting components, the circuit boards have good wide tracks with plenty working space and copper etchings don't easily part from the circuit board like many older sets.  Black Gate or Elna type electrolytics can be sourced on Ebay, but the voltage of the set's electolytics must not be increased, except in the reservoir capacitors and only then at most about 13 volts above Solid State stock.  Tube amps lie beyond the scope of this Guide.  Many Ebay electrolytics are now available and these shown above are the SAMWHA For Audio, one of the best smoothing cans presently available!  Don't take all sub-50 volt to be one family of electrolytic, only use the same voltage shown on the original cans from the set.  Take out a resistor and check its value on a meter to ensure your new resistors fall within the same resistor colour coded value, if not use a meter to replace all the resistors using the tolerance value printed on the resistor.  High resistance resistors break down in time so check you boards and know what you're running is good quality! 

The poor contact speaker twist grip connectors in Technics and Sansui can be replaced with screw down gold plated types, the screw is more rigid, it's the ideal connector.  The resistors are replaced with low distortion high stability Metal Film and Wirewound values, wirewound has little or no noise, as it's just a length of wire, always put in wirewound where possible.  The 0.25w carbon resistors in the signal lines near the volume control are the best first resistors to replace as this amplifies a much purer source.  The other resistors only slightly help if replaced, but may increase the life of transistors in the event of high resistances breaking down.  Yes all values may change and old bad solder is the first area for improvement, be careful you protect components from heat and leakage current. 

Such home improved relatively low cost Hi-Fi amplifiers are a lot better for it.  For instance the original Technics SU-Z2 will have dim power meter back lights that dip with bass power peaks and volume out will be quite poor.  After rebuild the power lit meters will be bright and after burn-in, the amplifier will be good and powerful enough to give top service on a REALISTIC speaker like the Mach Two or One etc!  Some folks think rebuilding low-end Hi-Fi is a bit of messing around as Integrated Amplifiers have a limited sound quality.  The semi-conductors and knob variable resistor distortions affect S/N ratio and Dynamic Range and are not easily replaced, but easy Rebuild MODifications can polish these old integrated amplifiers up to such a higher quality sound with CD etc, that you'd never go back to their original sound afterwards! 

Oriental Twin Powered amplifiers have much better stereo separation when working like new.  A few of these will need the solder replaced to get them working as good as they look - not an easy job!  The harman/kardon A 402 was built by  H i t a c h i  in Japan - and in 1978 that was the highest accolade! With amplifiers like the Sansui A 60, replacing the smoothing cans helps.  (see the two electrolytic cans behind the heatsink in the pix) and the inputs in the the pre-amp stage and in the volume control of the pre-power amp stage benefit from the old carbon composition resistors being replaced with low noise, high stability Metal Film types.  This brings them up to harman/kardon HK6200 standards as amplifying a purer source signal compared to original stock components that spoil the inputted quality, so improving S/N ratio for CD players etc.  Only perform mods on Sansui A 60 amplifiers if you cannot get the better Twin Powered sets quickly.  The late 1970s Twin Powered amplifiers only need the solder points serviced, their components were built to survive the test of time but best suited to 70s speakers, they're not amplifiers for modern Home Cinema use, their 'qualities' shine brightest with stereo late 1970s speakers when quality was higher.  'Ribbon wires' on high volume control Sansui A 60 style amplifiers, benefit from changing to screened core cable.  Be sure to keep an HK6200 for comparing your work progress, just be sure not to judge it by looks, if need be, shut your eyes and don't use a higher power model as their dynamic range is a lot less, almost -20db poorer!  Why?  -Lotsa reasons, one being all the up market features, not least higher power and component build cost limitations.  Amateur builders forget, that getting a high c/w copper heatsink on Ebay doubling volume cooling, or adding selected components, puts the price way out of market competition, oriental design is good under all the cut-cost parts to fit pricing points!

SANSUI A60 TYPE AMPLIFIERS:  SANSUI A40, A60, A80, Rotel RA 840, RA-860, SONY TA-AX3, TA-AX4, TECHNICS SU-V4, SU-V6, NEC A-520E, A-820E, NAD 3020, 7020.

If you buy new equipment the modern variable resistor components may not be fitted, instead some British amplifier designs did away with tone controls, some even dumped the balance control, as these impose a lot of distortion and noise even if their supporting circuit elements are upgraded!  But harman/kardon maintained high sound quality with full facilities, 'features cutting' measures in Britain, so proudly held by their media as the Japanese bowing to a British design lead, often meant a cost-cutting and profiteering exercise!  So rebuilding good oriental amplifier designs with even better quality components improves their already pleasant sound quality -but isn't cheap!  The REALISTIC STA-2000 will benefit from a rebuild but the internal construction is very nice. 

Announced in the UK - that analog switch off will be in 2015, there's protest but the government reckon when half the people have either digital front end or satellite equipment, they'll switch off Hi-Fi FM.  It's a brave political gamble and is surely going to discard a lot of good Hi-Fi sets, it's not as if these are like crystal radios or old television tube pictures! 

Rebuilding a STA-2000 is a bit like retrofitting a B52H, is it worth it?  Aged solder makes such servicing almost essential with silver harman/kardons but try running the STA-2000 in or doing just some solder like the power supply, its fuses and replacing the reservoir cans with the best you can afford on Ebay. De-oxit and Superlube can only do so much and the crackle that remains is the extra circuit resistance added by old solder!  TV Street Rod shows with obsolete cars, update old stuff too, but replacing ELNA electrolytics in the STA-2000 like the rebuilds on 60s Detroit cars, mean you'd better first renew all the old solder and do a run-in, to check they even need replacing! -$$$-  In fact harman/JBL have service info for A 402 rebuilds just as 50s and 60s cars get upgraded! 

harman/kardon A 402, Twin Powered

Sansui A 60 Single Powered

Sansui A 60