nc-300

[AE1CT]

my nc-300 plays real good on am but there is nothing on cw or ssb, is there any adapters i have to find or is there something wrong. i cleaned the band switch and all controls but still nothing, any ideas?

[Pete, WA2CWA]

There are no additional "adapters" that you need. Test the tubes; measure the voltages; look for loose or broken wiring connections. Typical trouble shooting activities. Did it work before you got it? Read the manual.

[AE1CT]

There are no additional "adapters" that you need. Test the tubes; measure the voltages; look for loose or broken wiring connections. Typical trouble shooting activities. Did it work before you got it? Read the manual.

yes it worked when i got it but now its dead on cw and ssb but am works great. i put all new tubes in it when i got it but never listened to ssb.

[nq5t]

yes it worked when i got it but now its dead on cw and ssb but am works great. i put all new tubes in it when i got it but never listened to ssb.

Be very suspicious of V8 (6BE6) ...

[MikeKE0ZUinkcmo]

First, be sure your BFO is running with a scope or check the voltages as noted above.  If its running, its most likely just off frequency. Follow the steps in section 4.2 of the manual.

[KM1H]

Id be suspicious of corroded socket pins as it is a common fault with that set. If the BFO is off frequency you should at least hear a different backround noise when switching between AM.

Carl

[kb3rdt]

check your screen resistors I have one was about same way low on ssb loud on AM...

[WB6NVH]

Tubes are not spark plugs.  Changing all of them is invariably a waste of money and can sometimes introduce new problems into otherwise good working equipment.

[WB2CAU]

Tubes are not spark plugs.  Changing all of them is invariably a waste of money and can sometimes introduce new problems into otherwise good working equipment.

The same goes for those that "re-cap" everything they get their hands on, especially within the audio crowd.  I only replace caps that are actually defective. 

[w3jn]

That very strategy cost me the power transformer in my SX-11 some years ago.

[KM1H]

Not replacing all paper caps and electrolytics in vintage gear is pure negligence. Power transformers are easily fried but so are audio transformers plus band and tone switches in some models.

I see the results in here all too often that has nothing to do with the audiophool crowd.

Carl

[MikeKE0ZUinkcmo]

Tubes are not spark plugs.  Changing all of them is invariably a waste of money and can sometimes introduce new problems into otherwise good working equipment.

The same goes for those that "re-cap" everything they get their hands on, especially within the audio crowd.  I only replace caps that are actually defective. 

Have to admit I've used the same "don't fix it if it ain't broke" technique for a few decades now without any serious disasters.  I do go through and check voltages after its been running for a few hours, do an alignment, and verify operation per specs, which are often a joke,  but that's it.   Mebby I just pick the wrong stuff, but an occasional disaster has got to be far cheaper than a whole new set of parts for every piece of gear one buys.

[WB2CAU]

Not replacing all paper caps and electrolytics in vintage gear is pure negligence. Power transformers are easily fried but so are audio transformers plus band and tone switches in some models.

I see the results in here all too often that has nothing to do with the audiophool crowd.

Carl

The paper caps are probably leaky, especially those black caps with thin color bands sometimes called bumble bee caps.  That qualifies as defective and a good reason to replace.  I will replace those caps and they usually always measure leakage. All caps can be tested.  

In my experience, older, defective electrolytic caps usually show higher (than normal) leakage currents before they fail catastrophically.   

I also have gone 40+ years with the philosophy of not replacing good caps and have not had any problems.  

Like I said, I will replace defective caps, not good ones.

[KM1H]

Unless you invest in often expensive test equipment you have no idea what the condition of most caps is. Blind luck just dont cut it any longer as the years roll by.

It is a whole lot cheaper to replace all those paper and electrolytics than just one transformer. Well out of tolerance resistors affect overall performance and trying to claim a receiver works fine without a thorough check is not the sign of a good tech or engineer.

[WB2CAU]

Unless you invest in often expensive test equipment you have no idea what the condition of most caps is. Blind luck just dont cut it any longer as the years roll by.

It is a whole lot cheaper to replace all those paper and electrolytics than just one transformer. Well out of tolerance resistors affect overall performance and trying to claim a receiver works fine without a thorough check is not the sign of a good tech or engineer.

Maybe it would be wise to invest in some good test equipment so you won't have to do shotgun repairs.

[Pete, WA2CWA]

Everyone has their own particular way of attacking a rig on the bench. I also have never done shotgun replacement of all caps since I got into this hobby. Caps hanging off the various power supply(s) voltage lines (high, low, bias, etc.) generally get my attention first after a complete inspection of all the wiring. Coupling, bypass,and frequency determining caps generally are further down the trouble shooting list after doing voltage and resistor value checks, alignment, etc. But, if you're in the business of repairing radios, the capacitor shotgun approach can give you piece of mind that the radio won't be returned any time soon, at least not for a capacitor problem.

[KM1H]

Maybe it would be wise to invest in some good test equipment so you won't have to do shotgun repairs.

Id suggest you read that while looking in a mirror.

I said nothing about replacing ALL caps and replacing just the paper caps and electrolytics is a long established procedure in any competent shop. That IS NOT shotgunning. In fact, the factory Service Dept at National did exactly that and Ive been doing it ever since.
Bumblebee, Black Beauty, and pink Sangamo caps were already failing in the 60's and other brands had various degrees of leakage affecting performance.

There is also a big difference between someone working on his own gear and more concerned about cheeep cheeep and someone that is doing it as a service and does not want returns to damage a high level reputation.

As far as test equipment, I have more than enough high end types to do any job. No TV/Radio basement shop low end hacker gear here.

[WB2CAU]

Maybe it would be wise to invest in some good test equipment so you won't have to do shotgun repairs.

Id suggest you read that while looking in a mirror.

I said nothing about replacing ALL caps and replacing just the paper caps and electrolytics is a long established procedure in any competent shop. That IS NOT shotgunning. In fact, the factory Service Dept at National did exactly that and Ive been doing it ever since.
Bumblebee, Black Beauty, and pink Sangamo caps were already failing in the 60's and other brands had various degrees of leakage affecting performance.

There is also a big difference between someone working on his own gear and more concerned about cheeep cheeep and someone that is doing it as a service and does not want returns to damage a high level reputation.

As far as test equipment, I have more than enough high end types to do any job. No TV/Radio basement shop low end hacker gear here.

Earlier in this thread, I had been referring to the "replace all capacitors" crowd.  If you peruse the audio bulletin boards you will find that to be an attitude that many audio hobbyists subscribe to.  In most cases those guys are hobbyists with little real technical background.  I have been a repair technician for the majority of my working career and I would not have been a very competent one if I replaced every capacitor on every product that crossed my workbench.  That would have been foolish, unnecessary, time consuming, and extremely expensive for the customer as it still would be today.  I think you can do much more damage to a reputation replacing perfectly functioning parts and charging the customer for it. 

What's with the "Id suggest you read that while looking in a mirror" remark anyway?  You have no clue about my workbench.  I have decent test equipment to find defective caps.  You had implied that it's cheaper to replace all caps than test because you'd need expensive test equipment.  I told you I have the equipment. 

I'm not suggesting that leaky caps should be left in products and ignored.  I'm all for replacing defective caps as I stated earlier on in this thread.  I'm saying it's pointless to replace good caps.  What's the argument, Carl?

[w3jn]

If a 60 year old capacitor isn't bad now, it soon will be when hit with voltage for the first time in 25 years.

The filter caps in the SX-11 tested fine when I had it open.  Minimal leakage.  Some months later I had it on while I went to dinner and started smelling something, shore 'nuff the filter caps shorted.  I was stupid and lazy.  Easiest just to replace the goddamn things while you have it open, spending a buck or so in caps.

This advice pertains to filter caps and non-ceramic bypass caps over 25 years old.

I found a TON of bad resistors in a WJ8716 I recently worked on, 1979 vintage.  Also, those mustard colored tantalums of that vintage go bad often also.   Every radio has its own strategy.

If you wanna cheap out on 5 bucks worth of caps and an hour of work to risk a power tranny it's no skin off my back.

[KM1H]

What's with the "Id suggest you read that while looking in a mirror" remark anyway?  You have no clue about my workbench.  I have decent test equipment to find defective caps.  You had implied that it's cheaper to replace all caps than test because you'd need expensive test equipment.  I told you I have the equipment.

Almost from the beginning I stated all paper caps and electrolytics...only. You might need glasses also.

For all I know your idea of a good cap tester is a Simpson 260. It isnt worth my time to individually test 20+ caps at their rated voltage since almost 6 decades of experience tells me they are crap. There are some exceptions but not in consumer grade radios, only experience will help in the exceptions and even then it is getting dicey these days with Vitamin Q's.

If I bought a tube radio from you that was claimed to be a full recap and there was even one unchanged paper cap I would call you up and call you a hack.

This is not an audiophool forum so why bother bringing it up repeatedly?

Am I getting thru to you yet?

JN has an excellent point about tantalums.

[WB2CAU]

If I bought a tube radio from you that was claimed to be a full recap and there was even one unchanged paper cap I would call you up and call you a hack.

We are in complete agreement on that, Carl.  That would certainly amount to misrepresentation.  Much like the guy who sold me a "new" variable cap on eBay.  The one I received was a totally misaligned one, obviously not the one pictured.  He was a hack too.  There are no shortages of hacks.  :-)