Saturday, November 26, 2011

A rare clear and warm day in November enticed me outside to snap a few shots of this Honeywell T6GA-600 galvanometer amplifier.

I'm speculating that this unit would originally be deployed between a sensor and a readout or graphing system, and I expect it to handle and pass DC. In passing a little time with the search engine, I found a patent application submitted by Honeywell five years after the build date of this T6GA in which they are attempting to solve the galvanometer frequency limitations (inability to operate in the 25,000 cps range). So, I haven't lofty hopes in regard to frequency response, even though 25 khz is off the charts for most people. I've been seeing a lot of references in the 100 hz range for standard, original purpose application, which DID include mechanical movement, so I'm hopeful that at least something will pass through this thing.

I found another document, published in 1966 under DOD (US Department of Defense, not the effects maker) contract dealing with "the Biological Effect of Blast from Bombs" which is just as gruesome as one would expect, in which the Honeywell T6GA is performing a supporting role between piezoelectric gauge signals and an oscillograph recorder. While they mentioned a low frequency response, I would venture that a percussive blast requires a certain level of prompt reaction, so I really don't know what to expect. I know, I know, just hook something up to it and pass signal already! Patience, we'll get there eventually.

The rear panel male XLR outputs were added by me, bypassing the originally wired Amphenol 20-27p multipin connector. I've yet to plumb male XLR connectors on the front panel as drilling metal in proximity to the actual circuitry hits my bad idea filter really quick.

Gutshot reveals an interesting quality.

Each of the six amplifier channels has a dedicated secondary winding, rectifier and 2000mf cap. Clearly crosstalk was not considered acceptable.

Even ground plane in the circuit is floating. The circuits themselves are pretty simple.

In no particular order: a 2N1395 Ge PNP

MHT1045 Ge PNP

and a 2N534 Ge PNP per channel, a couple mica caps, an axial cap (presumably paper & something), a few carbon comp resistors and what appears to be an opaque DO-7 but may just be a 1960s mystery part.


krivx said...

This is interesting, you don't come across much like this in Europe. There's another on ebay right now, is that where you scored this one?

crochambeau said...

Yup, this was from eBay, several years ago.

I wonder what European facilities do with their decommissioned tools? Has RoHS bottlenecked the trade in vintage equipment?

krivx said...

Afaik RoHS doesn't affect the vintage market. At least it's never come up when I've bought anything. The WEEE probably has more to do with it

The big difference is the lack of the military-industrial and manufacturing industries. I just got a great deal on a scope but it doesn't compare to the prices of cheap decommissioned test equipment I've seen on US eBay. There just doesn't seem the same amount of equipment kicking around.

crochambeau said...

OK, I wired it up and passed some drum track material through it. Aside from a little buzz (probably due to the old electrolytics) there was a subtle change in quality. I recorded through the Honeywell and through the headphone output of the Akai, normalled the levels and stuck snippets end to end: the impression of a bit of distance, bass & presence both dropped, and mid-bandwidth grain (ala the transistor radio sound) increased somewhat.

I didn't hit the Honeywell hard, and the batteries in the H4 decided to go belly up before I got that far, so it's hard to gauge at this point if there's a useful overdrive signature.

There is a faint DC component on the outputs of the T6GA, so coupling through a cap or transformer is advisable.

crochambeau said...

I find it odd that there's a lack of manufacturing/industrial (the US based stuff has practically evaporated, so I guess I shouldn't be too surprised). How close are you to the former Soviet region? The Hollywood polluted parts of my mind envision interesting stuff in that part of the world, assuming it's not still being used..

krivx said...

I live in Ireland, not much was made here and there wasn't a huge amount of research done until the 90s. There is a lot of stuff on the continent but you have to find it and pay for freight if it's heavy.

eBay is fantastic for small parts orders of Soviet stuff. I have hundreds of closely matched Ge transistors and some nice gas-filled thyratrons waiting to become distortions and oscillators.