[Ron Ramirez]

Restarting this thread at the request of John (Eliot Ness).

A few weeks ago, I bought a Fisher 700-T receiver from shopgoodwill. I've disassembled it and it is on my bench now, so here are a few photos from the shopgoodwill ad:

[Image: http://www.philcoradio.com/images/phorum...00-T_1.jpg]

[Image: http://www.philcoradio.com/images/phorum...00-T_3.jpg]

[Image: http://www.philcoradio.com/images/phorum...00-T_2.jpg]

The 700-T, 550-T and 500-T are often found with the lettering around the tuning and speaker select knobs worn off; sometimes, even the model number in the upper right corner is gone. The lettering on mine is not perfect, but is still readable.

The photos make the cabinet look much better than it is in real life. In reality, it is dull with a few small to medium sized pieces of missing veneer. It will require repair and refinishing. But as decent Fisher cabinets sell in the $100 and up range, and I paid less than that for this receiver including shipping, it's well worth the effort to repair and refinish.

I was asked why I'm doing this, and what I am going to do with them.

Why?

1. Because I like them as they are visually and technologically appealing to me.
   
2. Because they make use of the modern FM band.
   
3. Because I can.
   

What am I going to do with them? Simple - I'll fix them up, and then sell some, keep some. There is a growing interest in vintage stereo receivers of the 1960s, 1970s and 1980s - the sets made before the generic all-black appearance came into fashion. I think these are becoming the new "antique radios." I've been in the vintage radio hobby long enough that I can remember when a Philco 90 wasn't much older than some of my Fishers are now. In 1974, a Philco 90 was 43 years old. Today, it's 83 years old. In 1974, a Fisher 700-T was 7 years old. Today, it's 47 years old. Get the picture?

Where will I display them? Oh, I'm thinking of building some sort of cabinet to house the ones I intend to keep. We build shelves to display our vintage radios; why not something similar for stereo receivers?

But I have no intention of building up a huge collection of these things. Like I said...sell some, keep some.

[Ron Ramirez]

I put this on the bench last weekend, disassembled it and went to work.

One major mistake I made: I now feel it is imperative to test your audio output transistors before proceeding. I didn't.

More on that later.

I decided that on this one, I would replace every electrolytic capacitor and several of the paper/film caps as well.

This 700-T used four can-type electrolytics; two for the main power supply filters, and two as audio coupling caps to the speakers.

Taking what I learned from vintage radios, I rebuilt three of the four (for one, the replacement cap would not fit in the can but the replacement, a snap-in type, fit in the clip which holds it in place on the chassis).

Here's one of the audio coupling caps.

[Image: http://www.philcoradio.com/images/phorum...e00001.jpg]

The first thing to do is to carefully cut the can open, at the bottom but as close to the top of the flange (where the can's diameter is smaller) as possible. You'll see why shortly.

[Image: http://www.philcoradio.com/images/phorum...e00002.jpg]

Now, you are presented with the mess inside:

[Image: http://www.philcoradio.com/images/phorum...e00003.jpg]

Remove the old guts completely. Due to the size of the snap-in replacements, we need all of the room we can get.

[Image: http://www.philcoradio.com/images/phorum...e00004.jpg]

I drilled holes in the base, and added leads to the snap-in capacitor's terminals to go through these holes.

[Image: http://www.philcoradio.com/images/phorum...e00005.jpg]

Insert the new cap (make sure you get the polarity correct!) and close it all up, using glue to hold the can together. Notice how neatly the base fits into the top part, making use of that flange?

[Image: http://www.philcoradio.com/images/phorum...e00006.jpg]

Now, I reinstall the rebuilt cap in the receiver.

[Image: http://www.philcoradio.com/images/phorum...e00007.jpg]

The new one is on the right in this photo. The one on the left, as well as the input filter electrolytic, was rebuilt in a similar manner. These are held onto the receiver chassis with clamps, much like Philco electrolytics of the 1937-38 period, so it was important to reuse the old cans and mount the new caps as I did for space considerations.

[Ron Ramirez]

Here's a couple photos of two of the set's seven circuit boards that will be rebuilt.

The predriver:

[Image: http://www.philcoradio.com/images/phorum...e00008.jpg]

and the preamplifier:

[Image: http://www.philcoradio.com/images/phorum...e00009.jpg]

Notice there are several wires which are soldered to these boards. It is a challenge to remove and replace these boards due to all of the unsoldering and resoldering required. You have to make detailed drawings and/or take photos so you will remember which wire goes where...and you should only do one board at a time.

Photos of the rebuilt boards later.

[Ron Ramirez]

Last night, I finished rebuilding the second of the two driver boards, and decided to try the thing out before I move on to the MPX, IF, and control amplifier boards.

I discovered the power switch does not work. So, I temporarily soldered a wire across it.

Something told me I had better use a Variac to bring it up slowly.

It is a good thing I did! At 60 volts the two 0.68 ohm resistors connected to the left channel output transistors began to release the magic smoke.

I removed the power, disconnected everything, and immediately pulled the output transistors for testing.

One of the left channel outputs has a dead short between emitter and collector.

And the two right channel output transistors are not the correct type - someone replaced them with incorrect parts.

This is why I'm glad I bought that transistor tester...and why I will be checking output transistors from now on before proceeding to repair a receiver, so I will have a better idea of what I will be in for.

[Eliot Ness]

Very interesting Ron. Your analogy of the Philco 90 vs a Fisher is spot on age wise, and helps me put early audio into a completely different perspective.

Just curious what transistor tester you bought and how it is working out so far?

[Ron Ramirez]

John - It is a Heathkit IT-18. The seller sent it to me in a brown manila envelope with no padding!

Incredibly, it seemed to have survived OK. The only problem is that the meter needle sticks sometimes in the middle of its range. So does the needle on the meter of my Heathkit TT-1A tube tester. But anyway...I replaced the "D" battery with a fresh one and it was off to the races; it has worked ever since (with the exception being the needle that occasionally sticks). Oh, I also found the manual online, downloaded it, and calibrated the tester using the procedure given in the manual (which was a fairly simple process).

So, boys and girls, I promised photos of the rebuilt predriver and preamplifier boards.

The rebuilt predriver:

[Image: http://www.philcoradio.com/images/phorum...0003-1.jpg]

Only two capacitors were changed here - the two 1 uF tantalums were replaced with 1 uF electrolytics. All four transistors are new replacements.

Now, the rebuilt preamplifier:

[Image: http://www.philcoradio.com/images/phorum...0004-1.jpg]

New electrolytics and new 0.33 uF film caps. Four of its six transistors were replaced as well.

Here's a quick look at the underside of the 700-T, with mostly new capacitors (I had not started on the control amplifier board yet):

[Image: http://www.philcoradio.com/images/phorum...0001-1.jpg]

Now, a look over in the upper right corner. New rectifier diodes and new fuseholders. One fuseholder was broken; I replaced all three so they would look alike. They were cheap, from Mouser.

[Image: http://www.philcoradio.com/images/phorum...0002-1.jpg]

Yup, I bumped one side of the AC line with the soldering iron and will have to sleeve that bare spot.

I'm working on the control amplifier now. Its ten 1 uF radial electrolytics are stubborn and do not want to come out of the board. I'm ending up with some damaged pads as a result.

More to come...

[Ron Ramirez]

Just found, and bought, some ECG162 (Philips, not NTE) transistors since I did not have any suitable replacement audio output transistors in my stash. I am going to replace those 0.82 ohm resistors, also, as soon as I find some. I have no idea what the wattage is for those, and the service manual does not specify this information.

[Mondial]

Hey Ron, for future reference you do not need to change out the tantalums. The ones you replaced have a solid electrolyte and do not dry out or deteriorate. They basically last forever.

Tantalums also have very low leakage and tight tolerances, much better than aluminum electrolytics

Also a bit curious as to why you changed out the ERO film caps? Those are great quality caps and far better and more reliable than the Chinese replacements sold today.

[Ron Ramirez]

Really? Interesting...the guys at AK say just the opposite - that tantalums are not to be trusted.

It does not matter how many years' experience I have with tube electronics (and how many years it has been since I worked on any solid-state stuff)...with receivers, I'm basically a noobie...and enjoying it.

[Mondial]

Well, I am not sure where the person on AK got his info. Perhaps he was thinking of wet tantalums, which have an acid electrolyte and are prone to leaking. These definitely do deteriorate with age

Solid tantalums are typically used in long life military and test equipment where reliability is key. I have some surplus solid tantalums made over 50 years ago, and they test as if they were brand new as to leakage and capacitance tolerance.

[Ron Ramirez]

Wow...good to know. Okay, the next Fisher that crosses my bench will get to keep its tantalums, if it has any.

[Ron Ramirez]

While I wait for the ECG162s, here are a couple more photos.

The rebuilt audio control amplifier:

[Image: http://www.philcoradio.com/images/phorum...0002-2.jpg]

and one of the two rebuilt audio driver boards:

[Image: http://www.philcoradio.com/images/phorum...0001-2.jpg]

I'm not going to do anything to the FM-IF and MPX boards until I get the amplifier up and running again.

[Ron Ramirez]

The ECG162s are supposed to arrive tomorrow. So, this afternoon, I decided that I should test the transistors in the two driver boards just to be sure. Fortunately, all six tested OK.

I bought eight of the ECG162 transistors (four for this receiver, four for future use - the price was right so I didn't mind doing this). When they arrive, I think I will run all eight through my transistor tester and try to match up the beta on four of the eight as closely as possible, and use those in the 700-T.

[PhilcoMike]

Way to go Ron, restuffing vintage hi-fi caps!!

Mike

[Ron Ramirez]

Thanks, Mike!

I really hate the USPS. Why people still love an antiquated, inefficient system that is constantly losing money, can't deliver anything on time, or offer an accurate tracking system is beyond me. I'll stop here before I go political...but you should get the picture.

Anyway....they promised a delivery date of yesterday, and then today, for my transistors. And they only have to travel across this state. Guess what...no transistors yet.

March 31: Shipped from Middlebury, IN (northern IN). Sent from there to South Bend, also 3/31. From there they fell into a black hole...no further tracking updates so far.

So the waiting continues...