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 Post subject: Panasonic RF-5000
PostPosted: Apr Sat 16, 2011 7:15 pm 
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Joined: Aug Wed 19, 2009 1:33 am
Posts: 147
Dave Doughty:

You told us that you have this radio
Image

and also you told us that it's a TRF design in all bands as We can watch it here

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and here

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but you also told us that althought it's a good performer on sensitivity it is NOT that good....
May I ask why you think so ?... cause in my experience all TRF designs are great performers due to their resonant circuits.

Could it be due to the low gain Germanium transistors ?

Please elaborate a little more...THANK YOU !


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 Post subject:
PostPosted: Apr Sun 17, 2011 12:33 pm 
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Location: Utica, NY 13502 (USA)
I had an RF-5000 at one time. I sold it because, at my location among several high power FM broadcast stations, the shortwave bands were unusable. Front-end overload from these signals caused hiss and static across the entire bands. (This is a problem with many multiband transistor radios I have.) The SW bands worked OK when I tried the radio at another location. The AM and FM bands were OK at my location but I didn't like the audio sound compared to other radios I have.

Dave


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 Post subject:
PostPosted: Apr Sun 17, 2011 9:14 pm 
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Should be a no-brainer then, Dave, when it comes to deciding between staying in that neighborhood, or improving your radio's performances.... :wink:

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 Post subject:
PostPosted: Apr Sun 17, 2011 10:52 pm 
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Location: Utica, NY 13502 (USA)
The chance of my moving anytime soon is absolutely nil. I love where I live and the radios are secondary. The interference was much worse when there was a 1,000,000 watt UHF TV station on channel 20 whose tower was (and still is) on property next to mine. Now that they've gone digital with much less power, all of their type of interference (sync buzz getting into everything and anything electronic with a speaker) is gone. Hurray for digital TV.

The one radio that I'd like to find a way to filter the FM interference from is my Panasonic RF-2200. That, too, is totally useless on shortwave at my location. AM and FM reception, however, is superb.

One solid state multiband radio that is factory stock and free from overload interference is my Zenith R7000-2. That's probably why it's my favorite. The Royal 7000's are not immune. Their problem is mainly total overload across the FM band, itself. Shortwave on these is somewhat usable.

I have a Sony ICF-5100 Earth Orbiter which is good performer on all bands here but has no TRF stage. So whether or not the set has a TRF stage or not doesn't seem to play a role in the type of interference I have on some radios.

I rarely get this kind of interference on my tube radios.

Dave


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 Post subject:
PostPosted: Apr Tue 19, 2011 7:39 pm 
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Dave:

Is the Transoceanic R7000-2 you most sensitive radio ?


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 Post subject:
PostPosted: Apr Tue 19, 2011 10:44 pm 
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"Due to their resonance circuits"

The whole reason Superhets phased out TRFs is because the of an unavoidable issue with TRFs trying to get a bandpass filter effect is extremely difficult to do with a variable capacitor. This would require many many tuned stages. A superhet converts the incoming signal to a low fixed frequency and its very easy to make a fixed frequency band pass filter, which most standard superhets have 2, these are the IF transformers. Also you can build a higher gain amplifier more efficiently at lower frequencies. TRFs sound good because of the lack of the bandpass effect.

This TRF here has 3 tuned stages while the standard AA5 has 6 including the oscillator, which actually tunes the radio.

Another thing wrong with TRFs is no matter the band, the coils are going to be more efficient at higher frequencies, so sensitivity will be lacking at the low end. This can be covered up by good AVC but if youve ever listened to a late 30 4 tube TRF, you will be very familiar with this.

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 Post subject:
PostPosted: Apr Wed 20, 2011 1:58 am 
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Wcirco:

Don't get confused, we are dealing here with superheterodyne radios WITH a Tuned RF Stage but heterodyne the remainder of the IF stage, like these mentioned in this thread,
http://www.antiqueradios.com/forums/vie ... p?t=156112

by the way what's your most sensitive radio ?


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 Post subject:
PostPosted: Apr Wed 20, 2011 2:14 am 
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Hm you can see where I would have gotten confused because superhet was never mentioned here, only trf. My bad :lol:

My best radio is a 1 tuber I built with a 6418 tube. Its not the sensitivity that makes it great, its the selectivity. Im able to separate stations all the way up to 1500 or so and there are no stations that lay over each other.

My best transistor set is probably my Zenith royal 500. Pulls in everything very well.

Im into more of the early american and early japanese sets which none of them were real good radios in terms of performance.

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 Post subject: Re: Panasonic RF-5000
PostPosted: May Sun 20, 2012 3:38 am 
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Hi Guys .I'm new here.I dont see no since starting a new thread on the same radio model.Is this ok.I dont want to be a thread hijacker .I have that same radio.The Radio work great.Playable with good reception .But it has a moderate hiss in the background on all functions.the hiss is still there when the volume control is to zero.I got the schematic online last night.but its not really clear to see the parts values .I'm thinking its a noisy transistor or a cap that went sour.

Today I did some tracing and the radio signal is clean up to the volume control and the AF pre amp TR13 2sb173 is ok. The problem look like it rests around TR14 area which is a 2sb345.The hiss starts around the tone controls.I have not recap the area yet.I will post some photos when I get to it. Skip..


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 Post subject: Re: Panasonic RF-5000
PostPosted: May Sun 20, 2012 4:23 am 
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Welcome to the ARF Forums ! !

Recapping should clear that hiss up. While in there, check for poor or iffy solder joints.
Q-TIPS and isopropanol alcohol on the volume control is inexpensive and quite effective.

Post a photo of your radio when you can - we all enjoy seeing a classy chassis.

~ Mitch ~


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 Post subject: Re: Panasonic RF-5000
PostPosted: May Sun 20, 2012 12:58 pm 
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I think you may have a noisy TR-14. With three stages of audio amplification after the volume control (prior to the output stage), TR-14 would need to be an ultra-quiet one. Germanium transistors do sometimes become noisy (hissy) with age. But if that's not it, there might be a noisy resistor associated with TR-14's circuit.

Dave


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 Post subject: Re: Panasonic RF-5000
PostPosted: May Sun 20, 2012 3:00 pm 
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Dave Doughty wrote:
I think you may have a noisy TR-14. With three stages of audio amplification after the volume control (prior to the output stage), TR-14 would need to be an ultra-quiet one. Germanium transistors do sometimes become noisy (hissy) with age.


Based on recent experience, that's certainly where I would start. Bad capacitors cause a lot of problems but not usually a constant hiss. Whereas I have found numerous bad driver transistors that do exactly that.

Brett


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 Post subject: Re: Panasonic RF-5000
PostPosted: May Sun 20, 2012 5:22 pm 
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Thanks guys for the tips .I will check it out later today.


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 Post subject: Re: Panasonic RF-5000
PostPosted: May Fri 25, 2012 7:51 pm 
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Hi guys. Heres an update.Ok as I was checking things out the other day as I was trouble shooting the amp section.I found out what I mentioned with TR14 .TR14 is ok.I get clean sound through the tone circuit.I did replace C79 after TR15.TR15 2SB345 seems to be the problem.I got to look around for a replacement or a similar 2SB sub for it.meantime I'll recap the section to be safe.I will post photos when I get my Photobucket account squared away.Ok for a quick guess off hand.What other 2SB will be a good sub for 2SB345 .If I can't find one in my stock.I did a quick search on Google and found that some say 2SB56 will work.I don't have a spec sheet handy now to compare. Skip....


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 Post subject: Re: Panasonic RF-5000
PostPosted: May Sat 26, 2012 4:14 am 
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Location: Utica, NY 13502 (USA)
2SB365 and 2SB65 both cross to an NTE-102A in their database. The NTE-102A is a medium power, garden variety PNP germanium transistor. There are many other 2SB- types that cross to this replacement. Here is the data sheet:

http://www.nteinc.com/specs/100to199/pdf/nte102a.pdf

You can use this crossreference site to find a suitable replacement that you might have on hand:

http://nte01.nteinc.com/nte/NTExRefSemi ... f/$$Search

Dave


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 Post subject: Re: Panasonic RF-5000
PostPosted: May Sat 26, 2012 4:36 pm 
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Thanks Dave for the info.I will check it out.


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 Post subject: Re: Panasonic RF-5000
PostPosted: May Thu 31, 2012 8:17 pm 
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Hi .Will it was last sunday I got down to the bottom of finding out what was wrong with the RF5000 Yes it was a noisy transistor so I swapped the 2SB345 for a 2SB56 which my friend told me to try.It works great.No hiss.great tone response with the new transistor.Ok heres some photos of the radio.


Image


Amp bd

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Image


Back of radio

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Image


Chassis.




Image

Image

Image

Front


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Image

Parts replaced. 2SB345,Neon bulb which was on the ant input which the leads broke.10uf electro cap which was probably good.but replaced anyway.

Image


I found the AM bar ant is broke but the am still works but alittle dim reception.


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 Post subject: Re: Panasonic RF-5000
PostPosted: May Thu 31, 2012 10:17 pm 
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WPPCProductions wrote:

I found the AM bar ant is broke but the am still works but alittle dim reception.

A little crazy-glue will fix that.

apply the glue, then use some tape to hold both sides in place until the glue dries.

You might want to also make sure the antenna coils still have continuity.

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 Post subject: Re: Panasonic RF-5000
PostPosted: May Thu 31, 2012 10:51 pm 
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Location: Sunnyvale CA
WPPCProductions wrote:
Hi .Will it was last sunday I got down to the bottom of finding out what was wrong with the RF5000 Yes it was a noisy transistor so I swapped the 2SB345 for a 2SB56 which my friend told me to try.It works great.No hiss.great tone response with the new transistor.

<<snip pictures>>


I found the AM bar ant is broke but the am still works but alittle dim reception.


Just for my own edification, which one was it, 1st AF, 2nd AF, or Driver?

You can just glue the ferrite back together. They usually break very cleanly so even cyanoacrylate will work if it didn't break the wires at the same time. If it's free of coil I might clean it real well and put a doubler on either side of the crack with JB-Weld.

Brett


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 Post subject: Re: Panasonic RF-5000
PostPosted: May Thu 31, 2012 11:32 pm 
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Thanks fifties for the tip. I just some krazy glue for the car I will fix the bar ant tonight.

Brett.It's the 2nd AF anp transistor.



Image

I got a clean complete copy of the service manual from Bama.Link below if allowable.


http://bama.edebris.com/manuals/panasonic/rf5000a


The radio was ok to work on.But like any electronic stuff some bad words came out because the way they design the product for ease of the serviceman.It was a alittle tricky to get the amp board out without breaking those output transistor wires.Be carefull.

Thanks guys for the help.


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