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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Thu 29, 2018 9:58 pm 
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Thanks for the advice. I think I will go ahead and check the rest of the caps in FM section just to be sure, then give the oscillator coil a tweak.

I see the RCA 9-INT-1's and -2's show up now and then. Prices are all over the map. I saw a 9-INT-2 go for $10 in Chicago a few years back, but it was pick up only. The last one I saw was $300 with a beat up cabinet.

If I have to, I can live with the half FM band. What comes in sounds good, and my iPod sounds good through the tape input. So I will definitely get some use out of it.

I really appreciate your guidance through this project.

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Fri 30, 2018 2:09 am 
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Maybe cleaning the 12at7 tube socket and checking the connections there would help. Nice restoration.


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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Fri 30, 2018 3:54 am 
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Thanks, I will definitely check out the 12AT7 socket and connections as much as possible. The sub-chassis mounting makes it almost impossible to get at the underside without removing it.

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Sat 14, 2020 1:36 am 
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Ed did you ever figure out the issue with your FM on this radio? I recently picked up a 9INT2 (same radio chassis with an added turntable) and I have the exact same issue on my FM as you did. There must be a common faulty component on these.

T

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Sat 14, 2020 2:08 am 
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Sadly, I did not. I replaced virtually all the components, including the trimmer caps, in the FM section with no success. I had a restored Browning RV31 FM tuner, so I have it plugged into the tape inputs of the RCA for FM reception. It’s an excellent tuner and sounds great through the RCA. The Browning has several switched jacks, so I have a CD player connected through the Browning.

I also have a Zenith Cobramatic record player connected to the RCA. Basically, I use the RCA as the amp and speaker system for a hi-fi set in our den.

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Sat 14, 2020 9:28 pm 
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Ahhh that is too bad. These German sets all seems to use a very similar sardine can style FM front end unit and they all seem to have issues. I have seen-heard of several of the Graetz/RCA units with this exact same problem so there must be a component that is consistently failing on all of these. You would think someone out there would have stumbled across what the issue is by now.

The FM tunes with ferrit slugs and someone mentioned if it was possible the position of those or the coils have changed. Also I wonder if one changed the value of the trimmers you could bring the band back into range?

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Tue 24, 2020 7:39 am 
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Re reading through your thread tonight before digging into mine I have one question that was brought up but never answered. Did you ever end up trying to tweak-adjust the oscillator coil ? Towards the end you mention that was the only thing you had not done but then the thread went silent and no answer. You have me very curious..

Todd

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Tue 24, 2020 1:18 pm 
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I think so, but can’t remember for sure. I tried everything recommended. I replaced and adjusted trimmers and coils. No success. Very weird.

I was also getting some drifting on the FM stations that did come in, so running a good quality fm tuner through the tape inputs isn’t a bad compromise if you can’t figure out a fix. If you do, let me know.

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Thu 26, 2020 10:08 am 
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Ed Morris wrote:

I was also getting some drifting on the FM stations that did come in, so running a good quality fm tuner through the tape inputs isn’t a bad compromise if you can’t figure out a fix. If you do, let me know.


Hey Ed, I fixed mine last night! So like you I had great FM but my dial was shifted down some 5MHz. I was looking around under the cover of the FM front end. I took take several different size small mica caps 10, 48, 100pf and added capacitance to different spots. I noticed I could easily shift my band up and down the dial with adding capacitance in places in that front end circuit, mainly around my osc trimmer (C14) but turning that trimmer did nothing for me. I decided to remove the trimmer from the circuit to measure it and to see if I could jumper in a few different mica caps to change the position of the band on the dial.

I had zero luck using set micas soldered in place of the trimmer, could not even get a single station. So I tried testing the trimmer for value and it was stuck at around 10pf but while turning the trimmer back and forth I thought to myself I am only getting maybe 20% or turn from this trimmer. Being this is an odd German trimmer I was not sure if there was more travel to it or not and I (initially) did not want to force it pas that 20% she wanted to move. So while gently turning the trimmer side to side trying to get any change on my tester I put a bit more force and felt the trimmer let go with a POP. I instantly had 360 degrees of rotation now and could see value now change on my tester! So, I re soldered the trimmer in place and BAM I now have TONS of adjustment now on my FM dial. After about 30 seconds I had my FM dialed back in right on the nose, stations are still strong and clear and all in the right place on the dial now!

So my suggestion is go back to your radio and check C14 for a full 360 degrees of rotation, if not this might be the same issue with yours. Good luck and post here letting us (me) know if this tip helps fix yours too!

Todd

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Last edited by bastardbus on Nov Thu 26, 2020 8:57 pm, edited 1 time in total.

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Thu 26, 2020 3:02 pm 
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Todd, that is fantastic. I admire your perseverance. I can't remember if I tried forcing C14. Probably not as I would have been afraid of breaking it.

As much as I dread it, I will have to pull the chassis and give that a try. Not sure when I will get around to it, but I will definitely post an update on the results when I do.

Just to be sure, we're talking about C14 shown circled in red below, right? And it should turn 360 degrees?

Attachment:
FMC14.jpg
FMC14.jpg [ 232.46 KiB | Viewed 1937 times ]


Happy Thanksgiving!

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Fri 27, 2020 1:16 am 
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Hi Ed, yes indeed that is the one C14.

And no need to pull the chassis you can get to it super easy, just remove the back and the screw is right there on that FM unit. Just give her a tweak. And see that half moon shape, I had to rotate mine a full 180 degrees before I got all my stations in the place they were supposed to be. I am not sure how this got that far off but my console did have someone do some weird updates and mods to it so it might have been tweaked at sometime. But it is working great now and I have not even re capped it yet

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Fri 27, 2020 5:15 pm 
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Todd, I gave adjusting C14 a try this morning. No luck.

First, C14 was not frozen. It freely rotated 360 degrees. I tried adjusting the FM band by rotating C14 to different spots around 360 degrees several times. The best I could get was 107.3 coming in at about 98.7 on the dial.

I think probably other trimmers and coils in the FM section have been messed with. I'm reluctant at this point to start messing with it any further with my limited knowledge. I can live with getting FM through the Browning tuner.

I'm glad you got yours going, and thanks for sharing the tip.

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Sat 28, 2020 4:21 am 
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Hmmm, sorry to hear that. I found it pretty coincidental that both these same radios had exact same issue, it was worth a try!

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Sat 28, 2020 3:30 pm 
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Like you, I had tried replacing C14 with fixed value caps and even a new trimmer, but none were successful. Next time I have to do anything with it, I may experiment with adjusting the other coils and trimmers in the FM section. I've been watching for another chassis, too, I could use for parts.

The rotating AM ferrite antenna in mine is not very effective. I use a length of wire behind the radio for better AM reception.

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Sun 29, 2020 10:43 am 
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I will keep my eyes open around here for a chassis or spare parts radio for you.

I just did all the ERO caps tonight and most of the electros in mine. The two 50uf tested good and no leakage so I left that for now. My unit was working excellent from the get go even with the EROs in place but tested a few of them and found a few starting to get leaky up at higher voltages so just replaced all of them anyway. Did you replace those small plastic caps in yours? They are all very small values and similar to ceramic or micas so was not sure if those should be left alone or replace them as well. I have had a lot of those NOS and always good.

As far as the ferrite antenna, mine has the exact same issue as yours. I is working but is weaker then just a long wire. ...too bad because it is REALLY cool set up.

One other issue I did have was a slight background hum on AM and SW. It was not AC hum and it was not on FM. It disappeared when volume reduced. I would up finding out was the 6AK8/EABC 80 tube. I guess this tube has several sections and runs various functions detector for FM as well as AM DET/AVC and AF amp. I have a good one in another German radio and swapped em out and hum was gone. So I am on the look out-in need of a good (preferably NOS) 6AK8/ EABC 80 tube if anyone had one please PM me.

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Sun 29, 2020 2:19 pm 
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Todd,

The 6AK8/EABC80 can also be replaced with the 6T8/6T8A. I'm using a 6T8A in mine for V5.

As far as the recap, I only replaced the caps that had a paper wrapping and the electrolytics. I left the plastic ones in place. It looks like three resistors just below the electrolytic caps were replaced as well. If you haven't you may want to check yours in case they have drifted high. The resistors in the photo look like 1 or 2 watt resistors, but I may have used those because that's all I had in the values needed.

Attachment:
9intRecap.jpg
9intRecap.jpg [ 330.99 KiB | Viewed 1878 times ]

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Sun 29, 2020 11:22 pm 
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Ed Morris wrote:
Todd,

The 6AK8/EABC80 can also be replaced with the 6T8/6T8A. I'm using a 6T8A in mine for V5.


How well is that 6T8 working for you? I "heard" there is some slight difference and for optimal performance you want to use an actually 6AK8 but that is just "internet heresay".

It does make me wonder though why there is a 6T8 and a 6AK8 designations if they are identical tubes. The prices of 6AK8s are considerably higher then 6T8s so it does make me wonder is there is something to it.

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Mon 30, 2020 12:47 am 
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My radio came with the 6AK8 installed, but it was bad. I don't recall now how I ended up with the 6T8A. I know the 6AK8s have been out of stock at AES for a while, which is usually my first stop for a tube. The difference between the 6T8 and 6T8A, according to the RCA Receiving Tube Manual (RC-20) is that the 6T8A has a controlled heater warm-time for use in receivers with series connected heater strings.

I don't have any way to make a comparison between the 6AK8 and 6T8A. It works is about all I can say. It's possible that the 6AK8 may perform better. Maybe ask that question in the Tubes, Parts and Services forum and see if anyone can shed some light on the differences.

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Mon 30, 2020 3:40 am 
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I think I know how I ended up with the 6T8A. If you search for 6AK8 on EBay, most of the listings come back for the 6T8 or 6T8A. The few 6AK8 listings from U.S. sellers were $60 and up.

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 Post subject: Re: RCA 9-INT-9 Restoration, Update 11/28
PostPosted: Nov Mon 30, 2020 3:58 am 
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Hello Ed,
really nice radio and I would had done the same with those 47ufds too .
Sincerely Rich


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