Heathkit Complete Stereo System In Rack

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When a local audiophile offered up this item we just couldn't pass.

Just look at it! What great 1980's looking pieces with all the switches and lights.

A solid 9 in the "coolness scale", especially the preamp and the power meter with all the lights. No this is not quite an audiophile system but perfect for a game room, man cave, or other non primary listening room. Match this up with a highly efficient set of JBL's or similar vintage speakers and a vintage entry level Thorens and it's guaranteed to be a lot of fun.

These units were actually offered up as a kit if you had the skills to assemble the entire system piece by piece. All the manuals with schematics, parts lists, and instructions are also included with your purchase.

We performed a light service on each piece and found then to working nicely. We cleaned all controls and replaced a few stressed components in the power amp which can provide 125W into 8 ohms.

This item is currently local pickup only from our shop in Glen Rock, NJ 07452. You're also welcome to arrange your own courier as many clients have in the past via uShip.

Components include:

1) AJ-1600 AM/FM Tuner

2) AD-1706 Active Audio Processor

3) AP-1800 Preamp

4) AD-1701 Graphic Power Indicator

5) AA-1600 Amplifier

6) Wood Cabinet

Cosmetic Notes:

• The top of the power meter has significant scratching.
• Some handles show scratches and wear.
• One switch cap is missing on the power meter and the switch shaft is broken part of the way down. The switch still works but the shaft is too short to install a replacement cap.

The SkyFi Testing Process for Preamplifiers:

We start with a visual inspection of all internal components to make sure that there are no signs of heat stress or damage. Capacitors are checked for telltale signs of predictive failure including bulging, shrunken wrappers, or physical leakage. We also inspect the PCB’s for discoloration from resistors or transistors that may have been running hot. On vintage units we often spot check select capacitors for value and ESR.

When we first power on a preamplifier we connect its RCA output to a Sencore PA81 Power Analyzer which simulates real world loading conditions and gives us an oscilloscope interface. The first order of business is checking that the volume control works smoothly throughout its entire range with acceptable channel balance. This is accomplished by feeding a 1KHz sine wave into one of the preamp’s line level inputs while monitoring the preamp’s output on an oscilloscope. We then switch to a 1KHz square wave to test the tone controls, loudness function, and filters where applicable. During this step we are watching for equal alteration of the test signal by both channels. This also helps us identify dirty controls that will need treatment. Once the basic line stage functions are verified, we test each input individually. This is especially important for devices that use relays to select their sources. If the preamp is equipped with a phono stage we test that as well. We use an inverse RIAA filter which allows us to feed a reference test signal into the phono input with the proper RIAA equalization and level. A square wave or sine sweep is used to verify that the device’s phono stage is faithfully reproducing the RIAA curve. If the preamp under test has balanced inputs and/or outputs these are tested as well.

We finish up our bench testing with a listening test with our bench amplifier and reference speakers. During this test we check for hum or hiss that may not have shown up in earlier testing. We also check that all of the tone controls and filters perform as expected. If the preamplifier has remote control functions these are also tested. Preamps with tube circuits or complicated power supply topologies are connected at our long term test rig for extended stress testing under real world conditions.

The SkyFi Testing Process for Solid State Amplifiers:

We start with a visual inspection of all internal components to make sure that there are no signs of heat stress or damage. Capacitors are checked for telltale signs of predictive failure including bulging, shrunken wrappers, or physical leakage. We also inspect the PCBs for discoloration from resistors or transistors that may have been running hot. On vintage units we often spot check select capacitors for value and ESR.

If the amplifier passes visual inspection, we move on to a controlled power on sequence using a Sencore safety analyzer to monitor current draw in real time. Once the amplifier is determined to be safe to operate, we connect it to full AC mains for function and power testing. We connect the speaker outputs of the amplifier to a Sencore PA81 Power Analyzer which acts as a dummy load, DC offset monitor, and oscilloscope interface. We start with a low level 1KHz test signal at the amplifier’s input and slowly increase its amplitude while monitoring the output on an oscilloscope for signs of noise, clipping, distortion, or improper channel balance. We continue increasing the signal level until the amplifier reaches clipping. At this point we take an output power measurement and compare it to the spec sheet of the amplifier to verify proper performance. If the device under test has both balanced and single ended inputs they are both tested at this time. We finish off the bench evaluation with a 1KHz square wave check and a 20Hz to 20KHz sine sweep to assess the amplifier’s frequency response characteristics. This battery of tests will usually reveal if the amplifier has any issues that need further attention.

Before the device leaves the bench, we perform a listening test with actual music using a variety of preferred test tracks. Our benches are outfitted with familiar monitor speakers which help us identify inconsistencies that will not always show up on our test gear. The main things that we are listening for are hum or noise with no signal present, proper center image, clicks, pops, or any other obvious undesirable audio characteristics.

If the unit passes all of these tests it is moved to our long term testing rig where we simulate real word operating conditions for 6-8 hours. This allows us to monitor the unit for signs of thermal runaway or intermittent issues that only crop up when the unit has fully come up to temperature.

The SkyFi Testing Process for Tuners:

We start with a visual inspection of all internal components to make sure that there are no signs of heat stress or damage. Capacitors are checked for telltale signs of predictive failure including bulging, shrunken wrappers, or physical leakage. We also inspect the PCBs for discoloration from resistors or transistors that may have been running hot. On vintage units we often spot check select capacitors for value and ESR. Vintage analog tuners also have moving parts related to the tuning gang and dial string. These parts are inspected for smooth operation.

If the unit passes visual inspection it is bench tested for a handful of key performance parameters using a Sencore SG80 AM/FM Stereo Analyzer. The SG80 allows us to “simulate” an ideal radio station using precision test signals instead of music. This device, in conjunction with an oscilloscope allows us to properly evaluate the following parameters:

1.  AM Reception (Where Applicable)

2.  FM Mono Reception & Tuning Meter Function

3.  FM MPX Reception (Stereo)

4.  Dial Tracking - How accurately the tuner dial or display indicates the actual frequency of the broadcast being received.

5.  Stereo Separation - A properly working stereo tuner will have minimal crosstalk between the left and right channel.

6.  Sensitivity & Signal Strength Meter Function - By lowering the output of the SG80 we can simulate weak stations and determine how well the tuner will be able to pull in weak distant stations. This adjustment also helps us verify signal strength meter function.

If the tuner has acceptable performance related to the parameters above we connect the unit for listening tests with a simple dipole antenna. We listen for audio reproduction quality of local stations and evaluate how many stations the tuner can receive while we sweep through the dial. We are looking to verify that the tuner can decode stereo on strong local broadcasts and pick up a wide variety of local stations at the bottom, middle, and top of the frequency band. At this point we also test convenience features such as muting, filters, built in oscilloscope function, etc.

We finish up with an extended listening test on our long term test rig. We tune in a strong local station and monitor for drift over a 2-3 hour period.