EICO 147a Shorts and fails.

[eman.galvan8]

Hi all! New member here.

A couple of years ago my dad gave me an eico 147a Signal Tracer as a gift. I do some electronics for audio as a hobby and its a wonder working with it. I absolutely love it.

I moved houses recently and had to re-set my work bench. When I plugged the 147a to my bench outlet it blew my voltage regulator's fuse (FWIW a 9A, 250V fuse). As I had no failures previously I thought it might have been an issue with my bench's power outlet connector. I changed the 147a to another outlet and it turned on just fine.

In order to keep it in good shape, and givent the fact that I was re-setting my bench and giving maintenance to my other equipment I decided to recap it while I was at it. Only changed the non electrolitics as I was thinking of replacing the capacitor can later on (it does not get hot or anything), I did not deemed it necessary at this point. After this step I turned the unit back on, tested everything and it was working like a charm.

Decided to change the VTVM output, gnd, tst amp and tst speaker jacks for newer banana jacks so I could make use of those features too. Changing them was straight forward and Im sure everything is where it should be.

HOWEVER, after this, turned the unit on... waited for it to warmp up, magic eye came on nicely and suddenly... a spark. Turned the 147a's power switch off and my voltage regulator blew its fuse again. I do not have too much hands on experience with tube gear and Im a bit hesitant to get in there. I thought I'd ask around here for any pointers or tips as to where and how to begin looking for failures.

Let me know if any other details are missing. Thanks a lot in advance!

Emmanuel.

 

[magicmike]

I would suggest replacing the main filter caps and bring it up on an isolation transformer and dim bulb, I just replaced mine in a 147 and it only draws 250mA at idle. That and install a fuse on the AC line to protect your transformer. Electrolytics become shorts as they age.

 

[eman.galvan8]

Thanks @magicmike

I did as suggested with the filter caps... I already had a fuse installed and while checking it I realized it was hitting the chassis slightly but enough to cause a short. Fixed that and placed it properly and we are back on track.

Im really happy I get to work with the 147a hopefully for many years to come.

Cheers!

 

[magicmike]

Thanks @magicmike

I did as suggested with the filter caps... I already had a fuse installed and while checking it I realized it was hitting the chassis slightly but enough to cause a short. Fixed that and placed it properly and we are back on track.

Im really happy I get to work with the 147a hopefully for many years to come.

Cheers!

I just tried using shielded cables for the audio trace on my 147, I was easily able to pick up 40mV of audio from my generator while only having the unit at half gain. I'm impressed to say the least. My next test is to buy a cheap AM solid state radio and try out the set once I build the shielded probes. Also, watch the line voltage as it will jack up your B+ and smoke tubes. I doubled the power resistor and STILL have to run it on the variac at 110 volts.

 

[eman.galvan8]

I just tried using shielded cables for the audio trace on my 147, I was easily able to pick up 40mV of audio from my generator while only having the unit at half gain. I'm impressed to say the least. My next test is to buy a cheap AM solid state radio and try out the set once I build the shielded probes. Also, watch the line voltage as it will jack up your B+ and smoke tubes. I doubled the power resistor and STILL have to run it on the variac at 110 volts.

Oh wow! Yeah, its a fine piece of equipment I think. I have other EICO gear and I really like them.

Interesting pointer about the power resistor, I haven't checked that on my unit and I don't think I've checked or replaced any of the resistors yet. I am yet to get a variac and some other improvements for my workbench as Im just starting to work with tube gear. So far, fixing the 147a up and reading the manual has been a very gratifying experience.