Why recapping the AM and FM radios matters

[Mike Sweeney]

So on my 2245 that I'm getting very close to finishing now I got to the new LEDs ( Thanks Randy) and the front panel. I also got the AM/FM recapped and still need to cap the muting circuit. But, before the FM was washed out, weak and not very sensitive. The Stereo would light but not where it should relative to the meter. In the process of capping, I found 4 completely dead caps and most were at least 50% out of tolerance. Whatever life this Marantz had was very hard on caps. I have found dead ones all through the system. The two 1uf on the out of the FM card were replaced with films and all new electrolytics for the rest. Now the FM is punchy, great sensitivity and working awesome as is the AM. It also cleared some pops and crackles from the FM side. I also cleaned the air cap for the tuner and added some deoxit to the brushes that make contact on the shaft.

I've seen a lot of "restored" radios and cap kits that do not fix up the FM/AM side. Thats a mistake in my opinion. Yeah, it's a PIA bit but it's a nice finishing touch and FM is still alive for now

This is one of the coupling caps.. 15 ohms? ugh.. The new film is .5 ohms and within 5% of the value. Small wonder the FM sounded like crap

The LEDs are the "warm white" and it's hard to show the lighting for the indicator LEDs but they nice and bright and the red stereo is RED thanks to Randy's red LED replacements.

 

[jd3rdcoast]

Good advice. I should do that to my original 2245 that is sounding a bit tired in FM.

Is that a home made cap meter? Or just out of case.

 

[blhagstrom]

I've been recapping the tuner sections on receivers for quite some time now.
Just like the rest of the e-caps in a unit, the timer e-caps get old and out of spec.
Small e-caps in the audio path are the biggest impact to sound.
The small voltage levels of tuner signal would be very sensitive to poor cap performance.

A lot of internet "knowledge" says mucking with tuners means an alignment will be needed.
Real tuner alignment certainly in not a bad thing but finding someone with the skills and tools is difficult.

I have a high end vintage tuner that hag over $600 worth of "service" at a respectable shop.
Not one capacitor was replaced. WTF?

I can only guess that maybe they did some measuring and tweaked things to align the tuner to the drifted old parts and then royally screwed the owner on the invoice.

Every tuner I recap (e-caps) works better. Some much better.
It is a pain to do. Many small caps packed into a small space.

The one thing that should not be kicked with is the air cap (big fin thing)
The screws there adjust the mica caps and the factory setting should not be messed with.
There is no reason to tweak on those.

A clean air cap and new e-caps is a solid base for a tuner.
Any other issues are in the transistors and transformers.
Transistor fixes are doable.
Transformer fixes, not so much. Lack of parts.

 

[Mike Sweeney]

A lot of internet "knowledge" says mucking with tuners means an alignment will be needed.
Real tuner alignment certainly is not a bad thing but finding someone with the skills and tools is difficult

Agreed.. out of all the tuners I've done so far, the re-cap and cleaning have put everything back to where it should be and is "good enough". Now, could I tweak it up? probably because of resister drift maybe or maybe someone "aligned" it to the worn caps but I have not seen that yet.. So far after the recap/cleaning the tuners have been loud, sensitive and work so I dont bother. I do have the gear and I do have book on radio alignments for "modern" radios.. lol. I've done tube base AM sets but no FM as of yet. One of these days I'll get a sacrifice radio and have at it to see if I can work it out. I do know that you can risk ruining the radio with damage to the IF transformers with cracked or broken ferrite slugs due to them being stuck so who knows.

 

[Mike Sweeney]

Is that a home made cap meter? Or just out of case.

This is one of the cheapo Chinese sets. I use it for quick and dirty testing. A better tester is my old Heathkit cap tester that does a real leakage test. I've seen dozens and dozens of caps that pass ESR but fail badly on leakage. If the cap is rated at 65 volts and leaks at 10, no good. Surprisingly or maybe not, the big primary filter caps while old and drifting, tend to pass the leakage test. I replace them anyways more for future use and safety. They are plus 40 years old and definitely pass their expiration date

 

[Steven Tate]

I always recap the tuners on 22xx's, and I have never seen the alignment related performance deteriorate. But I have seen it improve (less stereo lamp flicker, more stable meter needle, etc.) Does it sound better? Well, yes, but it's hard to tell if that is from the tuner rehab or the audio rehab. I just know I feel better about it because 45 year old electrolytic caps are still 45 years old. With so many of them, there are bound to be at least a few out of spec.

 

[quaddriver]

are there any ecaps in the tuner that replacing them requires an alignment? generally by the time I hit ECs on a tuner board, you are way way past almost all of the aligning points. when you get past the discriminator and into the decoder, yes, replacing ECs has a beneficial effect. I also recommend finding all the silicon and Ge diodes in the thing and replacing the sets matched by voltage drop. when I got a realistic STA84 working in FM (very weak, poor tuning) I had to replace just about every voltage amplifier trans in the 'magic tune', every diode, and quite a few 1-10uf caps, as well as the output amp (for the tuner board) trans. it was all for the good. now it gets stereo lock on 1 bar indicated on the signal meter.

 

[Mike Sweeney]

are there any ecaps in the tuner that replacing them requires an alignment?

Not that I've seen so far. This also holds true for the Kenwoods I've done. In some cases, I've used films for smaller ECaps ( 1uf and under) without issue and good signal quality. I have not replaced the diodes as a matter of course. It's an interesting idea.

 

[tarior]

Electrolytic capacitors have little or no bearing upon the sensitivity or selectivity of a tuner. NO designer worth his salt would put them in a VCO or tank as they just aren't stable or accurate enough. Chances are that cleaning the tuning cap is what brought the tuner back to life.
Inspecting for and repairing cracked solder joints in the front end and IF section will often yield good results, and I consider it mandatory when servicing any receiver or stand alone tuner.