[Ron Ramirez]

Mondial

Regarding signal strength, I had the receiver tuned to the strongest signal in my area and the meter was indicating a solid 4 out of 5 when tuned in properly. I did play around with the stereo trigger control to no avail.

[Mondial]

Is Q404 in a socket where you can easily change it?

[Ron Ramirez]

Yes, I believe so...

I have new electrolytics for all of the boards now, as well.

[Mondial]

At his point I really think the LED is working as it should and the MPX decoder may need work or alignment. After all, you don't know if the MPX or stereo indicator worked properly before the bulb burned out either.

Do you hear any stereo effect when receiving the strong station? If there isn't enough 19 kHz signal to turn on the lamp fully, there isn't enough to activate the decoder circuit and you will only get mono.

[BrendaAnnD]

It also may just need an IF/discriminator alignment. The discriminator doesn't have to be very far off to disrupt the 19 KHz pilot signal.

[Ron Ramirez]

Mondial and Brenda, it appears you are correct. Last night, I converted my Fisher 4400 to use an LED stereo indicator, and it works. Too well. Discussion here.

So I'll be digging further into the 440. I think I'll go ahead and replace the remaining electrolytics, and then see how well this Sencore works as I attempt a full alignment on the thing.

[Ron Ramirez]

I'm expecting another 440-T to arrive today, which is going to be a (somewhat expensive) parts set. It has a good front panel which I will use in the one I am working on.

Since I have to remove the MPX board to replace electrolytics anyway, I might remove the MPX board from the other 440 and see if it is any better?

[Mondial]

Before switching the board, you can try to peak the 19 and 38 kHz coils with a broadcast stereo signal. Put a scope probe on TP401,402 and 403 and peak for max signal. At least you will get some idea if its close to being aligned.

[Ron Ramirez]

10-4...now if I can find my old Delrin alignment tools that I haven't used in decades...

[Ron Ramirez]

Okay!

I spent all afternoon replacing electrolytics in the 440-T. You haven't lived until you have removed a Fisher preamp board (several wires and grounding points have to be removed, then you remove four screws and pull the board) and then reinstall it. Good thing my 440-T parts set arrived today (and it is a rather ratty unit, but the faceplate is in pretty good shape)...it helped me confirm that I reconnected everything correctly on that board. (I would have drawn a diagram otherwise, if I didn't have another set to go by.)

The control amplifier board can be serviced...carefully...without having to be removed. It had no less than eight 1 uF radial lead electrolytics, and all eight were leaking electrolyte to a greater or less degree.

It still plays after all that, but the right channel still sounds muddier than the left.

I did miss four electrolytics in the audio chain - two 16 uF units in the output section, and two 1 uF axial electrolytics on the control amplifier board. I forgot to order any 1 uF axials, but I have some 22 uF caps to replace the 16 uF caps.

There is one lousy 4 uF electrolytic on the IF board, and two electrolytics on the MPX board. The procedure for those two will be the same as for the preamp board - several wires will have to be disconnected, four screws removed, and then the board(s) physically removed for service.

I did some looking this afternoon, and did not see my old plastic hex alignment tools. I am wondering now if they got lost over the past two decades. That, frankly, is very likely.

Well, I can get some more when I order more parts.

[BrendaAnnD]

Are there still decent quality alignment tools available out there? Seem every set I've bought in the past 15 years has been pretty much garbage. The hex alignment tools are the only ones that hold up for more than a single use. Those narrow slotted ones don't even work the first time, they just spin the end off trying to move the slug, and I end up using a jeweler's screwdriver to make the adjustments (and allowing for changes in inductance made by the metal tip).

[Ron Ramirez]

I guess I'll find out how good (or how bad) modern plastic adjustment tools are before long, as I'll have to get at least a hex alignment tool before I can think about aligning one of these units.

As for this evening's progress...

Removing the IF board, replacing the two electrolytics (yup, it had two, not one), and reinstalling took a good chunk of this evening.

At least the thing is still working...

That leaves the MPX board.

And then going back, replacing the two 16 uF caps in the audio circuit, then ordering some parts for the next receiver - to include two 1 uF axial caps to finish the control amplifier in this one.

[Ron Ramirez]

Progress report for today:

I pulled the MPX board early this afternoon. And I just had to try the MPX board from the 440-T parts set. Big mistake - I lost FM when I fired the unit up again. So I pulled that MPX board, put the two new electrolytics in the original MPX board and replaced the 2N2924 (Q404) with a known good transistor that had come from my 4400, and reinstalled. FM was back. Whew! Still no Stereo Beacon light, but I'll attempt an alignment in the near future. I'll have to either find, or purchase, a hex alignment tool first.

Four more electrolytics and then they will all be replaced.

The 440-T I bought mainly to get the faceplate is in really bad shape; it looks like it was run until it died the death from very bad, leaky electrolytics. I've decided that it will be a parts donor...that is, if anything other than the faceplate from it is any good.

[Ron Ramirez]

Progress report, or lack thereof:

During the summer Mike (Morzh) kindly gave my Sencore AM-FM alignment generator a good going over, so I set the long-neglected 440-T on the bench this past week and gave the IF section a complete alignment. (Yes, I now have a set of plastic alignment tools.)

I do not have a good schematic matching the 440-T's multiplex decoder so I am sort of stuck on that. It is difficult to check voltages and double-check the large multi-resistor unit in the middle of the multiplex board without the proper schematic.

So, this one went back on the shelf...I should probably pull it back down and give it a good RF alignment next, to get into practice with these solid-state FM receivers, now that I have a good generator (with thanks again to Morzh).

[Ron Ramirez]

Well, since I have (more or less) managed to get my 700-T going, I decided to revisit my 440-T.

It has heavy distortion in both channels, which I have traced to...the control amplifier board. Both channels go into the control amplifier clean, and come out dirty.

So I've pulled the control amplifier board from a 550-T junk set I have, and will do the same thing with it as I did with the board I put into my 700-T, and that is to replace all of the electrolytics and the 0.33 uF film caps. I will also go over every solder joint on the board, as I did with the 440-T board which I put into my 700-T.

As for the multiplex decoder...

I built a prototype multiplex decider based on the LM1310 chip, and temporarily installed that perfboard in this 440-T. It seems to work...at least, I can tell a difference between FM stereo and FM mono...but it does not produce sufficient voltage to light up an LED stereo indicator. And I hooked everything up according to the schematic I found online for the circuit used with this IC. ?????

However, since then I discovered that the original Fisher multiplex decoder board that was in this 440-T is the same board used in the 220-T. I have the 220-T service info, so if I have to go back to original, at least now I have some voltages on the 220-T schematic which I can use as a reference.