NOTE: This sale is for the adapter, 3 octal cables, and screws/nuts only. It does not include the Precise 111 tester, test tubes, meters, test leads, breakout plug, and pigtail shown in the pictures. They are for demo only and do not come with this sale.
This is a modernizing adapter with a collection of test setup charts for the modern Compactron, Novar, 9+1-pin miniature (B10G), and Nuvistor tubes. It also includes installation instructions for the second Octal socket that is exclusively used by the adapter. I wrote these instructions. (Schematic is not available.)
Installation is easy, you must know how to use a screwdriver and how to solder. You must turn off and unplug the tester before installation.
Pictures show the condition of the adapter, and results of some tests. These include:
17JM6 Compactron:
- 5,700 uMho (Gm) transconductance reading. The tube is good.
- 90% emission reading. The tube is good.
- 1.3 Amp filament reading. This is slightly above spec because the tube is tested with 20V on the filament instead of 17.
6DS4 Nuvistor:
- 5,200 uMho transconductance reading. 9,000 uMho is minimum. Tube is weak
- 29% emission reading. Tube is weak.
- 0.145 Amp filament reading. This is close to spec.
17GT5 Novar:
- 3,650 Gm transconductance reading. 2900 uMho is minimum. Tube is good.
- 77% emission reading. Tube is good.
- 0.55 Amp filament reading. 0.45A @ 17V = 0.53A @ 20V, Tube is good.
This adapter allows you to connect any tube pin, 1-12, to control grid, cathode, screen, plate, filament 1, or filament 2. The Compactron's anode cap can be connected to any pin with a jumper. Pin 10 is normally used in the setup charts. This configuration lets you accurately test the Gm and Em of all Compactrons except possibly the 6EF4 and the 6EJ4, depending on the manufacturer's internal connections.
When properly working and calibrated, the Precise 111 is one of the most capable and accurate Gm testers. Plus it's one of the few combined Gm / Em testers. Aside from its accurate transconductance readings, its emission readings are not the simple combined grids plus plate test. It's like the EICO 666 & 667 Dynamic Conductance test. You can use it to match tubes.
This modernizing adapter lets you test "modern" vacuum tubes, most notably Compactron Sweep Tubes often used in high-power linear RF Amps. Precise has an excellent procedure for adding unknown tubes to the test charts that will work well with Compactrons. I will add notes describing how to set up Compactron tests for unlisted tubes.
Because of its simple pin interconnect method, the Precise 111 makes it possible to measure the plate current (Ip) and plate & screen voltages (Vp & Vg2). This feature lets you characterize a tube's operating characteristics, and makes tube matching even more accurate. The last 3 pics show how this is done. The first of the 3 is a 6L6GC measured for Ip, Vp, & Vg2. The red meter shows Ip at 65.2mA, Vp is 118.0V, and Vg2 is 142.1. Simultaneously you see the Gm of 6,000. Notice the Precise 111 tester (not included) is able to deliver 65.2mA to the plate. The plate voltage sags to 118V, but hey, not many other testers can do this.
What's nice about the Modernizing Adapter is that it extends this capability to Novar, Compactron, and even Noval tubes. You can't easily measure Ip of a 6BQ5 / EL84 because all pins are either used or reserved for internal connections. So there's no easy way to jumper the plate to the plate voltage source. But the adapter gives you pins 11 and 12 that can be connected to the plate voltage (selector 4), and used to connect the meter to the tube. (This setup isn't shown in the pictures, LMK if you need the details.)
Matching Sweep Tubes for plate current could be important. The next picture shows a 6GV5 Compactron wired to measure the operating characteristics. I use the 9-pin Noval socket to tap the screen and plate voltage pins. The tube measures 32.6mA Ip, 136.3V Vp, and 129.0V Vg2. The Gm is 4,600.
Finally, the last picture shows a 17GT5 Novar. This is a 9-pin tube, so all pins are accessible on the Noval socket. You just have to select 8 for the plate and switch O, select 4 on switch Q, and connect the milliammeter between the PLATE jack (negative) and pin 12 on the Compactron socket. The readings are 18.9mA Ip, 142.5V Vp, and 126.1V Vg2. The Gm is 3,300.
I had a lot of fun running these tests.
PLEASE NOTE: My Precise 111 Tube Tester, the test tubes, meters, test leads, breakout plug, and pigtail shown in the pictures are for demo only and do not come with the tester.
Returns accepted for items in same condition with all accessories. Buyer pays return shipping.
LMK if you have any questions about this listing.