Forums :: NEW! Web Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Oct Fri 22, 2021 4:19 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 66 posts ]  Go to page 1, 2, 3, 4  Next
Author Message
 Post subject: RCA 9-INT-1 Restoration, Update 11/28
PostPosted: Nov Sat 03, 2018 12:14 am 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
I bought this RCA 9-INT-9 table radio manufactured for RCA by Graetz in what was then West Germany (mid-1950's) from a fellow ARF member back in 2009. At the time, I didn't feel competent to try a restoration.

Attachment:
RCAg1.jpg
RCAg1.jpg [ 234.72 KiB | Viewed 4145 times ]


In the last two years, I have restored a similar AJA German table model radio, and two Philips B5X43A radios, so I thought I would finally give the RCA a try.

The first thing I noticed when I pulled off the back is that both the AM and FM dial cords were broken. There were three or four bits of cord loose. The steel dial cables were intact. My stomach churned at the thought, and was almost ready to give up before I even got started, knowing how complex the dial mechanisms are on these European radio

Attachment:
RCAg2.jpg
RCAg2.jpg [ 158.08 KiB | Viewed 4145 times ]


Attachment:
RCAg3.jpg
RCAg3.jpg [ 105.82 KiB | Viewed 4145 times ]


Fortunately, I had acquired over the past nine years a SAM's Photofact and an RCA service manual for the radio. Included in my documents was the dial cord diagram. Also, the AM dial indicator was broken. So my first task was to repair it.

Attachment:
RCAg4.jpg
RCAg4.jpg [ 222.81 KiB | Viewed 4145 times ]


I fabricated the missing ear from styrene plastic and glued it to the dial pointer with super glue.

Attachment:
RCAg5.jpg
RCAg5.jpg [ 150.27 KiB | Viewed 4145 times ]


I found after some study that the restringing of the dials was not all that complex. The AM and FM dials are separate, but operate off the same tuning shaft via a clutch mechanism. Pressing one of the piano keys (AM, SW, or FM) engages or disengages the clutch to engage the proper tuning mechanism for the band selected.

While the path isn't complicated, actually doing it is. The dial back plate makes access to the AM tuning capacitor drum difficult, and there are many ways to get the cord tangled up. While the FM drum is easy to work on, the AM drum has to be held with the plates half-meshed.

I found this very difficult, and ended up wedging a piece of wood between the drum and backing plate to keep the drum from shifting. When I would get the cord properly strung, the steel cable would slip off the drum or a pulley, and vice versa.

I found myself using hemostats, masking tape, and clips to hold things in place. Half the dial stringing uses cord, the other half steel cable. This is true for both AM and FM.

Attachment:
RCAg7.jpg
RCAg7.jpg [ 135.76 KiB | Viewed 4145 times ]


Attachment:
RCAg8.jpg
RCAg8.jpg [ 167.78 KiB | Viewed 4145 times ]


It took me from 10:00 AM until 2:30 PM to get both done. Most of the time was restringing the AM section. I did the AM first, and ended up doing it three times to get it right. The FM only took once and went very fast.

The dial diagram doesn't tell you how to install the dial pointers, so I lined them up with the low end of the AM and FM frequency bands. I don't know if this is right, but when I get the radio working, it is easy to move the pointers to a more precise location.

Attachment:
RCA9g10.jpg
RCA9g10.jpg [ 146.11 KiB | Viewed 4145 times ]


My next step will be to pull and check tubes and order any that I need. I also need to see what capacitors I will need. I plan to replace the electrolytic caps first, then see if the radio works. Then I will do a replacement of the remaining paper caps and check resistors.

I will post updates as I go along.

_________________
Ed


Last edited by Ed Morris on Sep Wed 01, 2021 11:18 pm, edited 7 times in total.

Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1
PostPosted: Nov Sat 03, 2018 12:42 am 
Member

Joined: Aug Sat 01, 2009 2:23 pm
Posts: 1913
Very good, Ed! You've gotten past one of the most frustrating tasks in any German radio restoration, and it appears you still have your sanity. The rest should be fairly routine. Just make sure you get all those bad ERO tan and black caps out of there, along with the dried out lytics and selenium bridge, and you should be good to go.

_________________
John Stone
Antique Radio Club of Illinois


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1
PostPosted: Nov Sat 03, 2018 3:04 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 4226
Location: Eschew Obfuscation Virginia 23005
Ed:

Nice find! I've always thought that this model RCA is a often overlooked as a good performer. I look forward to your next steps.

BR,

Terry


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1
PostPosted: Nov Sat 03, 2018 3:29 pm 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
Thanks, John and Terry. I hadn't thought about replacing the diode bridge. Are these diodes in the photo selenium? Can I use 1N4007 diodes to replace the OEM diodes?

Attachment:
RCAg11.jpg
RCAg11.jpg [ 191.99 KiB | Viewed 4073 times ]

_________________
Ed


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1
PostPosted: Nov Sat 03, 2018 6:49 pm 
Member

Joined: Aug Sat 01, 2009 2:23 pm
Posts: 1913
Ed..the original selenium bridge has already been replaced. Those are ECG silicon replacement diodes. You can pop in some 1N4007 if you want to, but the ones in there are probably fine as they are. I would put some resistance between the output of the bridge and the first filter cap...say 100 ohms @5 watts, to make up for the difference in internal resistance between the selenium and silicon rectifier bridges. It helps to lower the surge current at turn on.

_________________
John Stone
Antique Radio Club of Illinois


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1
PostPosted: Nov Sat 03, 2018 11:05 pm 
Member

Joined: Jul Sun 09, 2006 3:11 am
Posts: 7633
Location: Clearwater, KS
You're a brave man. My unit had a clutch problem on the tuner I never could fix. The FM section could have worked but the AM section had an issue. Good job!


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1
PostPosted: Nov Sat 03, 2018 11:22 pm 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
John,

Thanks for the clarification on the rectifier bridge. I will probably leave it alone. I will add the surge resistor.

Aurora,

Thanks. I need to do some more work on it. The AM worked fine until I restrung and added the FM. I have cleaned and lubricated the clutch mechanism, but one dial pointer wants to drag the other along for a short distance when I tune from low to high frequency. I guess the clutch isn't fully releasing from one mode to the other. And there's a lot of backlash now on the AM going from high frequency to the low end. I will need to play with it some more and see what's going on.

_________________
Ed


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1
PostPosted: Nov Sat 03, 2018 11:51 pm 
Member

Joined: Jul Sun 09, 2006 3:11 am
Posts: 7633
Location: Clearwater, KS
Ed Morris wrote:
John,

Aurora,
Thanks. I need to do some more work on it. The AM worked fine until I restrung and added the FM. I have cleaned and lubricated the clutch mechanism, but one dial pointer wants to drag the other along for a short distance when I tune from low to high frequency. I guess the clutch isn't fully releasing from one mode to the other. And there's a lot of backlash now on the AM going from high frequency to the low end. I will need to play with it some more and see what's going on.

Yep, that was the problem I had. I sold the radio and swore off German made models.


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1
PostPosted: Nov Mon 05, 2018 4:34 am 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
I tested tubes this weekend and found the 6AJ8 bad and the 6AK8 not much better, and the EM34 is totally dead. I've ordered replacements that will be here next week. In the meantime, I decided to go ahead and replace the electrolytic and ERO paper caps, which I finished up today. I had all the caps I needed on hand, so didn't have to order any.

Attachment:
RCAg12.jpg
RCAg12.jpg [ 217.74 KiB | Viewed 3972 times ]


Normally I prefer to re-stuff the topside can, but the two 47uF cans were too big to fit, so I mounted a terminal strip under the chassis for the two big filter caps. It looks like the radio may have suffered an event at some point as two of the paper caps connected to the 6AK8 were badly charred.

Attachment:
RCAg13.jpg
RCAg13.jpg [ 150.37 KiB | Viewed 3972 times ]


I also discovered and repaired a broken wire coming from the power transformer, which possibly could have been broken getting the chassis out of the cabinet, although I am not sure. Luckily I spotted it while looking for capacitors.

Attachment:
RCAg15.jpg
RCAg15.jpg [ 159.17 KiB | Viewed 3972 times ]


Finally, I decided to install a connector between the leads from the chassis to the speakers in the cabinet to make it easier to remove the chassis in the future.

Attachment:
RCAg14.jpg
RCAg14.jpg [ 136.83 KiB | Viewed 3972 times ]


While waiting for tubes, I will begin checking resistors in the next step.

_________________
Ed


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1, Step 2
PostPosted: Nov Mon 05, 2018 7:38 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 6043
Location: 253 Blanche St. Plymouth, MI USA
Those cap ends are not charred, but how they often look. Change all the paper and electrolytics anyway.
Note there is a fine calibration line at the end of the dial.
Take your time, these German sets are a pain but real nice radios when done well ! Nothing like them was offered in the USA. We see a lot of the German sets in the Detroit area, they were heavily imported 1957-1964
Mark Oppat


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1, Step 2
PostPosted: Nov Mon 05, 2018 1:48 pm 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
Thanks, Mark. I did note those calibration marks on the dial scale.

_________________
Ed


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1, Step 2
PostPosted: Nov Mon 05, 2018 5:11 pm 
Member

Joined: May Sat 06, 2006 4:03 am
Posts: 3606
Location: ZIP 23831 South of Richmond, VA 25 miles down the pike.
Ed, just in case here is a link to SAMS service data for RCA models 9-INT-1 and -2. There has to be a lot of similarities between the two. Might help some. I would bet the dial stringing is the main reason a lot of these sets don't get restored. But I believe you're one who can.

Bill J.

https://app.box.com/s/0e6dapvtu4ybgbfmbdka


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1, Step 2
PostPosted: Nov Mon 05, 2018 7:02 pm 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
Thanks, Bill. I may have to redo the AM stringing. I think I may have too much tension, causing the backlash.

_________________
Ed


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1, Step 2
PostPosted: Nov Tue 06, 2018 12:48 am 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
I solved my tuning problem. I found that the FM drive cord had slipped off a pulley. Now the backlash is gone and each dial tracks separately, no dragging each other along.

In studying the dial drive train, it seems obvious now that before I went to all the trouble to restring the AM and FM dials, I should have disassembled the tuning shaft mechanism and cleaned it.

There are two gear driven shafts turning inside each other and a clutch mechanism operated through a cable and lever actuated by pushing one of the piano keys to select an AM band or the FM band. Like the cycling mechanism in a record changer, it really needs to be cleaned to function flawlessly. I don't know if a lubricant was applied to the shafts when the radio was manufactured, but I cleaned away some built up gunk that could have been a lubricant at the bottom of the shaft where it connects to the cable.

The when no key is pressed, or any AM key (BC, SW1, SW2), the cable is in its default position, and the fingers of the clutch grasp the AM drive gear. Turning the tuning knob moves the AM dial pointer across the dial.

Attachment:
RCAg17.jpg
RCAg17.jpg [ 205.82 KiB | Viewed 3878 times ]


Pressing the FM key retracts the cable and a lever, which engages the FM tuning shaft and the clutch fingers release the AM drive gear and grasp the FM drive gear.

Attachment:
RCAg18.jpg
RCAg18.jpg [ 207.73 KiB | Viewed 3878 times ]


Reluctant to undo all my work to disassemble and clean the tuning shaft, I found some openings that allowed me to spray some De-Oxit into the inner and outer shafts, and that seems to have improved operation.

As John recommended, I also added a 5 watt, 100 ohm dropping resistor between the diode bridge and first filter capacitor.

Attachment:
RCAg16.jpg
RCAg16.jpg [ 147.42 KiB | Viewed 3878 times ]

_________________
Ed


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1, Step 2
PostPosted: Nov Tue 06, 2018 5:54 pm 
Member

Joined: Aug Sat 01, 2009 2:23 pm
Posts: 1913
Ed, Did you actually manage to find an EM34 that wouldn't cost you an arm and a leg? I always replace those with much cheaper eye tubes like the Russian 6E5 or a 1629 with an extra small transformer to power the 12volt heater.

_________________
John Stone
Antique Radio Club of Illinois


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1, Step 2
PostPosted: Nov Tue 06, 2018 6:05 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 4226
Location: Eschew Obfuscation Virginia 23005
jmsent wrote:
Ed, Did you actually manage to find an EM34 that wouldn't cost you an arm and a leg?


Amen to that!

BR,

Terry


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1, Step 2
PostPosted: Nov Tue 06, 2018 6:53 pm 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
Only relatively speaking. Most I saw ran about $100. I found a NOS Amperex (made in Austria) on eBay for $60 with free shipping. I read up on the Russian 6E5S or 6E5C, but preferred to stick with an EM34 even though the cost is more. Like most of my radios, I plan to keep and use it, so I don't mind investing a little more time and money in it, within reason.

Tested NOS Amperex 6CD7 EM34 "Magic Eye" Tuning Vacuum Tube Austria, USA Seller

Attachment:
EM34.jpg
EM34.jpg [ 117.31 KiB | Viewed 3854 times ]

_________________
Ed


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1, Step 2
PostPosted: Nov Fri 09, 2018 9:52 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 6043
Location: 253 Blanche St. Plymouth, MI USA
add a switch to the filament line of the eye tube... keep it off for the long listening hours and turn it on for tuning. It will last forever that way.
Mark Oppat


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1, Step 2
PostPosted: Nov Fri 09, 2018 10:44 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3625
Location: Nr London, England, SS1 3PT
Interesting thread for me as I have never done one of those. My interests stop at 1939. But you never know one may come my way and I would be tempted. Must be much better to find one untouched; after the Phantom could be even more difficult.

thanks Gary


Top
 Profile  
 
 Post subject: Re: RCA 9-INT-9 Restoration Step 1, Step 2
PostPosted: Nov Fri 09, 2018 5:15 pm 
Member
User avatar

Joined: Jul Sat 15, 2006 3:54 am
Posts: 3322
Location: Zeeland MI
I have one of those RCAs, a Grundig Majestic and one other German radio. They are off-putting for me. I guess it's the complicated (to me) mechanisms that make me not want to tackle them. The Grundig worked back in the 1980s, but quit several years ago. But that RCA is massive.
RW

_________________
"Never pay more for an acquisition than you have to."- Ferengi Rules of Acquisition #3


Top
 Profile  
 
Post New Topic Post Reply  [ 66 posts ]  Moderator: sofaslug Go to page 1, 2, 3, 4  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 35 guests



Search for:
Jump to:  


































Privacy Policy :: Powered by phpBB