RCA 4VF464 Restoration

[jheu02]

very nice!

especially that can cap restuffing is first class.:thmbsp:

oh, one thing i noticed is that looks like those two output tubes are close to dead with all the getter flash gone.

I did order a matched quad of Russian tubes from the 'bay, and have been playing them, but the RCAs still did sound really good, so who knows? :scratch2:

Thanks for all the kind words. Now to find some bayonet and wedge bulbs, scrub the wood with steel wool and the Watco equivalent of Restore a Finish, and load everything back in. I also found an Akai DS-5 Tape Deck Selector at a ReStore. It allows for 4 sources to be hooked up, so since the console only has the one "line level" switch position, I may fit this into the console or sit it on top to allow multiple input sources. I'm also going to run the tuner antenna hookups to a pair of screw terminals on the back so I can use my roof-mounted antenna through a 300ohm matching balun.

Anyone know what I should be looking at component-wise to tame the bass a little bit? It seems a touch boomy when hooked up to the tuner/pre as compared to using my Proton as the preamp.

 

[larryderouin]

Haven't got into my tuner yet. It's sitting in the corner of the Living room, and I play it once a week. FM in Stereo volume drops to almost nothing after about 20 minutes, but in Mono it's fine. Haven't recapped the tuner yet, so it's in there. When I get the $$$$ I'll go over the whole thing. Did get a RP217 from another AK'er. Just a bit of dirt on top. Motor and idler in good shape. Cleaned up nicely.

Larry

 

[jheu02]

Haven't got into my tuner yet. It's sitting in the corner of the Living room, and I play it once a week. FM in Stereo volume drops to almost nothing after about 20 minutes, but in Mono it's fine. Haven't recapped the tuner yet, so it's in there. When I get the $$$$ I'll go over the whole thing. Did get a RP217 from another AK'er. Just a bit of dirt on top. Motor and idler in good shape. Cleaned up nicely.

Larry

If you have an extra platter (or one that will work with this model) with decent rubber let me know. Mine was so brittle with age that it busted all apart while trying to get to the locking bolts. I guess I should at least hook the TT up and see if it works before proceeding further. Since I don't listen to albums all that often, it's not critical.

 

[larryderouin]

Mine came with a POS Plastic Fantastic BSR. Had to Put a wanted ad in Bartertown.

Put up an ad on BarterTown. I got more than a few offers for RP-217/218's. There are 9 and 11 inch versions so make sure you note what size yours is. Got mine for shiping only.

Larry

 

[jheu02]

Thanks for the idea about BT. I'll hook it up to see if it even works before doing so though.

 

[jheu02]

Help Needed with Dropping Plate Voltage

I'm wondering if I need to drop my plate voltage a little, and if so, what should I change out? Here's the schematic.

Here's the voltages I measured.

I'm thinking I need to change the value of R429, R430 (4W 130ohm) resistors, but the voltage I read on the cathode is pretty spot on. So, I guess I'm wondering which figures I should be plugging into Ohm's law to drop from my measured ~346V to 330V? Which resistors govern the resulting plate voltage? Do I need to look further "upstream" at the 6FQ7s?

Pics of finished "standalone" setup. The feet screw into the handles for easy disassembly and installation back into the console. I just had to make the holes in the chassis more of an oval shape with spacing slightly closer to each other to allow for the center-spacing of the handles. Base is just a 3/4" thick rectangle of plywood which I added red oak veneer edge-banding to. I had scrounged some perforated metal that was put out on bulk trash day, so I cut and wire-brushed some to cover the opening.

Thanks

 

[larryderouin]

John; R429 and R430 govern your bias voltage. It should be 11V R427 would govern your plate voltage. However the given voltage is 340, not 330 as you listed. What is your line voltage at the plug. If higher than 120, take it down to 120 and check again. also check the 6V filament voltages and make sure they stay btwn 6.0V & 6.3V.

If you change R427 you also change the B+ down stream of R426 for the grids and R425 to keep the downstream B+ the same or close to same as before.

You're only about TWO (2%) PERCENT high on the plate voltage. Manufacturers normally gave a variance of 10%-15% based on input voltage of 117VAC and differences in parts and tubes. My 3VF405 (RS177H amp)schematic states and I quote....

Voltages measured to chassis ground with VoltOHMyst and should hold within +/- 20% with 120V power source

.

So you should be ok as you are.

Hook her up and ROCK OUT!

Larry

 

[jheu02]

John; R429 and R430 govern your bias voltage. It should be 11V R427 would govern your plate voltage. However the given voltage is 340, not 330 as you listed. Larry

Thanks Larry. Since I'm right at 11V I won't do anything with those. What I was trying to figure out was how to drop the plate voltage from 346V to around 330V. I had a tube redplate on me, though it ended up being a tube issue since it followed the tube upon swapping. Line voltage is 120.8V and measurements were with a DMM not a VTVM so I guess that could also account for the higher readings.

What is your line voltage at the plug. If higher than 120, take it down to 120 and check again. also check the 6V filament voltages and make sure they stay btwn 6.0V & 6.3V.

If you change R427 you also change the B+ down stream of R426 for the grids and R425 to keep the downstream B+ the same or close to same as before. Larry

Since I just finished the base and buttoned everything up, I guess I'll leave it be. but if I understand you correctly, multiple resistor changes if I change out R427... Out of curiosity, and to help my understanding, I'd increase R427's value and then adjust the other's accordingly?

You're only about TWO (2%) PERCENT high on the plate voltage. Manufacturers normally gave a variance of 10%-15% based on input voltage of 117VAC and differences in parts and tubes. My 3VF405 (RS177H amp)schematic states and I quote....
.

So you should be ok as you are.

Hook her up and ROCK OUT!

Larry

Have been and enjoying it immensly. Last night a bunch of jazz from a local college station. I put my H/K T-403 (recapped and with a nice warm sound, though not the most selective or sensitive tuner) and just loved the presentation, especially of some of the live recordings they were playing...bass strings, cymbal brushes... Then listened to Bryan Ferry's Mamouna with all it's little sonics.

 

[larryderouin]

Thanks Larry. Since I'm right at 11V I won't do anything with those. What I was trying to figure out was how to drop the plate voltage from 346V to around 330V. I had a tube redplate on me, though it ended up being a tube issue since it followed the tube upon swapping. Line voltage is 120.8V and measurements were with a DMM not a VTVM so I guess that could also account for the higher readings.

DMM vs. VTVM probably Not. It could be tired tubes, not drawing enough current, which will let the plate voltages be high. Your RCA tubes could be tired. As your line voltage is right on(for all intents and purposes) I'd leave it, or drop the line voltage with a bucking transformer. Radio shack has a 12V CT 3A transformer that works nicely as a bucking tranny. You get a 12V or 6V drop with it, using the Center tap gets you a 6V drop. I've got one on my 800C using the 12V tap for the 800c and the 6V tap for my AKAI GX370D. If you do this, recheck the Filament voltages, and the bias voltage.

Since I just finished the base and buttoned everything up, I guess I'll leave it be. but if I understand you correctly, multiple resistor changes if I change out R427... Out of curiosity, and to help my understanding, I'd increase R427's value and then adjust the other's accordingly?

That's correct. The resistors drop the voltage in stages, but are interconnected as to results. Change the upstream one, and you need to change the rest downstream to compensate.

Have been and enjoying it immensly. Last night a bunch of jazz from a local college station. I put my H/K T-403 (recapped and with a nice warm sound, though not the most selective or sensitive tuner) and just loved the presentation, especially of some of the live recordings they were playing...bass strings, cymbal brushes... Then listened to Bryan Ferry's Mamouna with all it's little sonics.

 

[Blast]

I see we both have good taste in handles! :yes:



Good job on the makeover!

 

[getone]

The southern way

Put it (the whole thing) in the oven on a cookie sheet. Preheat to 170 or the lowest setting your oven goes. put the tuner in with the guts facing UP! and let it simmer for 3-4 hours. It won't hurt the dial cords. After cooking, set it aside for a couple hours to cool down.

Serves 8-10.



Larry

Here, in the Deep South we do this by parking the car outside for an hour, put the amp in and keep the car in the sun for 3-4 hours.

Today it is 103 F here...

 

[ericc129]

Old thread, but man I'm so envious of your work on this amp. Freakin stunning. I just recovered the exact same console this week. My RS177J amp was right next to yours on the assembly line with the number 63266; what strange odds. Seeing that you are also a Proton fan, I'd just about be willing to throw in or bribe you with my beloved Proton D-1200 amp, etc. just to consider restoring my RCA amp, even without the external aesthetic (although I really dig that paint job/color with this amp.). I'm just drawn to this amp for some reason; I hope it doesnt sit in my closet for years or just rot away while I learn how to do more than just swap out capacitors as an upgrade.

btw, I know its been awhile; but if you still need that platter, I've got one from my console ya can have. It was my friends grandmothers....I can't believe it was hours from going to the landfill before I rescued it.