[Ron Ramirez]

This morning, a new idea occurred to me - since Q1 and Q2 reside in sockets and are not soldered in place, why not switch Q1 and Q2 and see what happens?

So, I did.

In doing so, I caught a serious mistake I had made - I had installed the (incorrect) replacement for Q2 incorrectly. Amazingly, the NTE123 equivalent is still good - and when I had both reinstalled in the sockets opposite where they had been, I turned the thing on - and was immediately blown away by loud music from both channels!

So, now that I know it is OK, I can proceed with new electrolytics - and I will still purchase a new 2N2924 since the transistor now in the Q1 socket is not an equivalent transistor.

This is going to be a really nice unit.

Thanks to everyone for the help. And I will still order the manual.

[TA Forbes]

Self induced pain. MAN..... have I been there and done that!!!!

[morzh]

I hope not voluntarily - we have a name for it

[BrendaAnnD]

I hate it when I do that (all too often).

In the next few weeks, I have a really good chance to screw things up... had to order an NTE 703A for a Kenwood 5150 receiver. Lots of extra wires to put into the wrong holes.

I really shouldn't need to repair this receiver at all.. I bought it for parts for the one I had already (missing knobs, missing thumbscrews, etc.), but the doggone thing was partially alive, and I just couldn't leave it that way. The amp is in great condition, the tuner section was all but dead (totally on AM, a tiny bit of signal making it through on FM), so I had to track it down. Found that signal was good going into the IF amp IC, but nothing much coming out. I bypassed the IC with a 100pf cap, and got a nice solid FM signal and good stereo (shows how doggone sensitive these receivers are!). So, now I ordered a couple of the IC's and will put it all back to good working condition. Sometimes I'm my own biggest PITA.

PS, the reason I bothered to get the first one was that I knew about this particular receiver from owning one back when I was about 21 or so. They're really hot tuners. Not one, not two, but THREE RF stages for FM and one for AM. Special broad tuned AM IF's for better fidelity, yet still have good selectivity. The amp ain't bad, either.

[morzh]

So this IC might be a dud...

[Ron Ramirez]

Well, next up on my bench is a Fisher 440-T. Same size as the 4400, but not as nice looking. This one is actually more on the rough side with dirty knob caps, and lots of wear on the front panel around the volume and tuning knobs. It has an all but dead left channel. I'll post photos of it when I start a new thread on that subject.

And I had better get busy and rewind Tom (TA)'s coils before I start on the 440-T.

[Ron Ramirez]

Electrolytics have been ordered for the 4400 and my 440-T. I had to get a mix of Panasonic, Nichicon and Vishay caps...and had to get 85 degrees C in many of the values as Mouser did not stock 105 degree C electrolytics in many of the values I needed...so the 85 degree caps I bought have a higher working voltage than the originals.

I was going to start a separate thread on the 440-T, but I can summarize it in one sentence: It needs electrolytics...badly. The left channel audio makes it all the way to the coupling electrolytic just before the speaker. No audio on the other side. Both it and the right channel coupling electrolytic have dried electrolyte coming out of the vents at the bottom of each. Long overdue for replacement. It, like the 4400, will also receive new electrolytics in its power supply as well as the audio section.

[morzh]

Ron


For this application I don't think you really need 105C although I am surprised - I always find good caps in Mouser.
The amp you have with Ge transistors of this kind of power is not going to get too toasty inside.

[Ron Ramirez]

It took about an hour and a half to negotiate Mouser's quirky online parts search and put my order together.

I was finding zero results for some searches, so I tried it with just a cap value and "axial lead" specified...no working voltage...and when I did that, I often found the WVDC I was looking for that the parts search was telling me had zero results when I put in the WVDC also.

I miss the good old days of the printed catalogs...

[morzh]

Mouser search engine takes a little getting used to, yes, and sometimes it has errors in it too.
I just use it often enough at work so I kinda got proficient with it....
And you needed axials....I take it using cans was too inconvenient to try? Those often have better selection.

But as I said....your application does not necessarily require 105C.
Of course the more the better, the temperature affects the life span way more than voltage does.

[PhilcoMike]

Mouser is good but I have found Digikey's parametric search to work much better on capacitors.

[morzh]

Well.....this is Mouser 105C 1500uF 50V axial cap in stock.

http://www.mouser.com/ProductDetail/Corn...rgCSr6I%3d

Yes it is almost 8 bucks a pop, but then you only need two.

http://www.mouser.com/ProductDetail/Corn...rgCSr6I%3d

This one is 40V and 2200uF which is fully adequate considering it is at half-point. 105C. Stock.
And it is $4.62 a pop.

[Ron Ramirez]

As replacements for the large cans in both Fishers, I purchased Cornell-Dubilier and Panasonic "snap-in" electrolytics, not finding any other can-type electrolytics.

http://www.mouser.com/ProductDetail/Corn...FuCw%3d%3d
http://www.mouser.com/ProductDetail/Pana...UAJg%3d%3d

Both are 105 degrees C.

The other electrolytics being axial, have axial replacements on the way.

I tried Digi-Key but the first few values I punched in were not bringing up suitable replacements, so I stuck with Mouser.

Well, I have a half dozen or so more receivers that will need to be recapped, so perhaps I will spend more time on the next order.

LED festoon lamp replacements are also on the way for the dial scales of both, from eBay. I'll need to do some more research on LED replacements for the Stereo Beacon lamps in both. The 440-T uses a 47 lamp to illuminate the tuning meter. I will have to open the 4400 back up to see what it uses. Every bulb in the 440 is bad; most in the 4400 are still good but will be replaced with LEDs anyway, for longevity.

Oh, I am replacing the 1 uF coupling electrolytics with 1 uF metalized film caps. They are somewhat larger than the originals, but I thought they would be better long-term.

[morzh]

As long as the device gets used regularly (not left in storage for 10 years) coupling electrolytic caps are almost immortal as they do not see any real currents going through them and their temp is always at the ambient.
Obviously if not used they develop typical leak that could only be cured by reforming but with those it is not worth it as they are mere pennies in prices. If not replaced they screw up the DC biasing of the transistors they couple into which though probably won't burn anything will get distortion to increase.

Electrolytics are used there probably due to the fact that they cost very little and film caps could cost you many times that.

Let's take 1uF / 50V caps.

For example, this aluminum cap is $0.09 apiece. (the cheapest of its kind in Mouser)
http://www.mouser.com/ProductDetail/Lelo...aLVWvPk%3d

But this film cap is $0.63 apiece (also cheapest of its kind, same voltage / capacitance)
http://www.mouser.com/ProductDetail/Arco...dYmxyHI%3d


Now imagine you are in the business of building consumer electronics and you need an inter-stage cap in quantities of a few hundreds of thousands to millions.
Or (in some very mass-produced devices) - tens of millions and up.

[Ron Ramirez]

Agreed...but I'm not Avery Fisher. I'm just an enthusiast.