This article will discuss repair and calibration of the Jackson 561 tube tester. High voltages are present, repairs should only be attempted by a qualified technician. Copyrighted, all rights reserved.

Introduction

The Jackson 561 appears to be a rare (uncommon) model. Very little documentation exists, and I have seen only a small number of them for sale.

The model 561 is a combination of the Jackson 634 and the 648. Photo below shows Jackson 561 (right); Jackson 648A (left).

Comparison: Jackson 648A vs 561

If the 634 and 648 mated, the 561 would be its offspring. It shares the following characteristics from the 648: (a) the same meter, (b) variable leakage control, (c) color scheme, and (d) case design. From the 634, it shares (a) the same test method (which Jackson calls “Dynamic Output”), (b) Shorts Test control, (c) lack of a Noise test, and (d) function control layout. In fact, the 634 tube setup chart can be used (with slight modification) with the 561, as explained later.

(more…)

©2008, Bob Putnak.  All rights reserved.  This article discusses the B&K 707 Dyna-Jet Dynamic Mutual Conductance tube tester, including repair and calibration. The discussion is also relevant to the B&K 700 (the 700 is almost identical except for socket configuration) and some of the information is applicable to the B&K 650.

BK 700

my BK 707 with custom TubeSound plate current meter upgrade

The B&K 707 tube tester dates from the late 1960s into the 1970s. My manual is stamped August 1969, and a modern tube data setup chart dates 1978.

First of all, a brief explanation of the circuitry of this tester is necessary. Is this a Mutual Conductance tube tester? Well, yes and no.

Tubes that test in the “Jet-Check” section test for mutual conductance, with the exception of diodes/rectifiers (which always test only for Emission). The Jet-Check section is the upper panel (sockets 1 – 35). Tubes that test in the “Switch” section — the bottom panel (sockets 36 – 45), are tested for Emission.

(more…)

Kenwood KT-917 Pulse Count Detector FM tuner

Some people believe that the Kenwood KT-917 is the finest FM tuner that was ever manufactured. This is truly the cream of the crop. Pulse Count Detector, high build quality, Made in Japan.

A fellow in my community decided to trade-in this KT-917 for some quality tube audio gear. He had his eye on some nice tube gear in my collection, and his KT-917 needed repaired for quite a long time. Since he was currently more enthused with rediscovering his music tastes (vinyl and CD), he decided to forego repair and trade for tube gear.

Repairing the KT-917 was straightforward. The tuner was not decoding, and some quick troubleshooting revealed a defective MC1496 IC, which is a Balanced Modulator-Demodulator designed for FM detection.

(more…)

This article will discuss repair and calibration of the Jackson 648-series tube tester. It will also discuss the procedure to eliminate the 1S5 tube from models 648 and 648A. High voltages are present, repairs should only be attempted by a qualified technician. Copyrighted, all rights reserved.

Introduction

The Jackson 648 was available in several versions, including 648, 648A, 648P, 648R, 648S, 648-1, 648-1T. The basic circuitry is fundamentally the same in all versions, with only minor changes (socket layout/configuration, adjustable grid leakage circuit in 648-1T).

original 648 with tweed-style case

"newer" 648 model with 648A color scheme

648A model

648-S

648-R

648 Tweed-style case

648S with flipover socket panel

I am a big fan of the Jackson 648. It is definitely one of my favorite tube testers. While it does not employ a mutual conductance test circuit, it does use an advanced emission circuit that applies separate element voltages to each tube element, and separate load circuits are also used. “These voltages and loads have been carefully selected for each tube to meet most ideally the normal operating condition of the tube.” (Source: 1950 Jackson catalog).

In my experience, the Jackson circuitry is very effective, and often will surprise you with accuracy that approaches Hickok’s coveted “mutual conductance” test method.

Example: testing a weak 6N6-MG (metal envelope) triode tube:

(as tested with calibrated Jackson 648A)

(above: the same 6N6 triode, as tested on the Good-Bad scale of my calibrated Hickok 6000 mutual conductance tube tester)

Here is another comparison:

(more…)

Sencore Mighty Mite solid-state tube testers (TC28 Hybrider, TC162, and TC154) are durable, easy-to-use, and test a wide variety of modern tubes (including modern sweep tubes such as #8950). They were VERY popular among old-timer technicians. For most people , they are a very good choice.

Sencore TC28 Hybrider

Sencore TC162

Sencore TC154



Regardless of model, all the Mighty Mite solid-state models use the same basic circuitry, albeit configured slightly different among each model.  Model TC162 is functionally equivalent to B&K 607 / 667.

(more…)