I have completed the electrical restoration of one Hickok 209A VTVM. This included:

Replacing all the paper and electrolytic capacitorsReplacing all the carbon composition resistors (most were out of tolerance)Installing a polarized AC plug, line fuse and proper safety capacitorReplacing the meter movement (original was mechanically damaged)Rebuilding and restoring the battery holderBalancing the bridge tube resistorsGiving the unit a full check on all modes and ranges

With all of the above complete I can declare the unit ready to use. The cabinet still needs to be cleaned and refinished, but that will have to wait until warmer weather arrives and I can work outside.

The results of my testing were very interesting. I used my lab equipment (see below) to check the 209A on all of its ranges and modes (with the exception of the decibel range). … Read More »

This is the sixth part of an “N” part series documenting my restoration of the Hickok 209A VTVM, SN 1333254.

Hickok 209A VTVM Restoration Part 6: Component replacement decisions

In this Part 6 of the series I will document the condition of the passive circuit components in the Hickok 209A VTVM, and justify why I decided to replace (or not replace) them.

Initial resistor and capacitor measurements Hickok 209A

Starting with the resistors, I measured 8 initially, and of those 5 were out of marked specification on the high side. One more was right at the high side specification and two were within specification. These were all 5% and 10% tolerance carbon composition resistors. Based on these data, I made the decision to replace all the 5% and 10% carbon composition resistors. I used 1% metal oxide resistors with … Read More »

This the fifth part of an “N” part series documenting my restoration of the Hickok 209A VTVM, SN 1333254. Hickok 209A VTVM Restoration Part 5: Checking the meter movement.

This piece of test gear is all about the large, beautiful meter movement, so I need to determine if this one works properly. What I intend to do is connect the meter to a precision power supply and good ammeter through a current limiting resistor and then determine how the meter responds. The meter is supposed to be a 500uA full scale movement.

Here is the test setup:

Analog Meter Test Instrumentation Setup

A 10kohm limiting resistor is connected in series with the power supply. The power supply is a Tektronix PS5004 and the meter is a Tektronix DM5120.

Full Scale Deflection on the meter was about 497 uA:

Analog … Read More »

This the fourth part of an “N” part series documenting my restoration of the Hickok 209A VTVM, SN 1333254. Hickok 209A VTVM Restoration Part 4: Restoring the battery holder.

In Part 3 of this series I documented the condition of the D Cell battery holder and outlined the restoration plan for the unit. The first step is to remove and restore the corroded battery holder.

Hickok 209A SN 133254 Corroded Battery Holder

Besides the obvious corrosion, the white connecting wire to the negative terminal was corroded under the insulation from the battery spring clip to the switch solder lug. I replaced the entire length of this wire. The other short wire and ring terminal were cleaned as described below.

Hickok 209A SN 133254 Corroded Terminal Wire

The process I used to restore the battery holder:

Desolder the two … Read More »

This the third part of an “N” part series documenting my restoration of the Hickok 209A VTVM, SN 1333254. Hickok 209A VTVM Restoration Part 3, corrosion issues and restoration plan.

As mentioned in Part 2 of this series, a visual inspection of the chassis of the 209A revealed a serious corrosion problem with the battery holder. The corrosion had migrated to the bottom of the case but not to the remaineder of the chassis. There were no batteries in the unit when I received it.

Hickok 209A SN 1333254 Battery Holder Corrosion

Hickok 209A SN 1333254 Battery Holder Corrosion

Hickok 209A SN 1333254 Battery Holder Corrosion

Hickok 209A SN 1333254 Battery Holder Corrosion

From the above images, it is clear that the battery holder will require some corrosion mitigation and restoration. Fortunately, it is restorable as the parts are … Read More »

This the second part of an “N” part series documenting my restoration of the Hickok 209A VTVM, SN 1333254. Hickok 209A VTVM Restoration Part 2, visual inspection.

Outside visual inspection results:

Overall good visual condition outsideMeter appears to move freely and does not stickMeter face is excellent and there are no scratches on the glassMeter bezel is dirty, but does not appear to be corrodedArea of corrosion noted at bottom of caseThe case has some minor paint scuffs and nicks accumulated over the past 60 yearsLine cord appears to be original and looks to be in good conditionHas an original rubber grommet where the line cord enters the caseNo obviously broken parts: lamp, pin sockets, dials are in good conditionHas DC Probe (reads 3.36 Mohms)No AC probe but does have the 4 wire AC probe connectorNo pin tip test … Read More »

This is the first installment in a multi-part series documenting my restoration of a classic Hickok 209A VTVM. First a description and some images:

This is a Vacuum Tube VoltMeter (VTVM) with a nominal 12 Mohm input impedance and one of the largest mechanical meter movements found on commerical/consumer equipment (viewing area about 8.5 inches diagonal). It was produced from about 1947 (earliest direct evidence) to at least 1961 (catalog reference). One of the units I have has 03-09-55 written in grease pencil on the back of the meter movement. The cost in 1947 was (reportedly) $133 USD which is about $1500 USD in late 2018. In comparison, the HP 410A (a lab grade instrument) sold for $245 USD in 1948 or about $2500 USD in late 2016 dollars. So the Hickok 209A was not aimed at the laboratory … Read More »