R-388...What have I done?......

[RolandSWL]

Hi All,

 I finally have an official B.A. radio. I found an R-388 in good condition from a private seller and pulled the trigger.
 It arrived U.P.S. in a very sturdy box with scads of bubble wrap, peanuts, and foam blocks around the radio. I was sweating as I remembered the R-390A disaster of last year. This radio is lots lighter than R-390A which helped it survive the trip.
 I examined it for damage and found none. Off to the spare bedroom/radio cave for a run up on a variac. I undid the wing nuts holding the top cover and removed it. Checking for loose parts I found the plug in electrolytic unseated. It seems the hold down plate is AWOL. Plugged it back in and now ready for some A.C.
 Switch in STANDBY, variac to 70VAC, feeble glow from tubes and dial lamps. Go feed the cats. Return and bump the voltage to 100VAC.
Tubes almost fully bright now, resist the temptation to switch ON. Wait another 30 minutes, no smoke or sparks. Go for ON.
 By now I have a speaker wired up to the 4ohm terminals. Fingers crossed, switch ON and.........nothing. No hum,no static, no nothing.
What have I done? I did what years of working with electronics had taught me. Where there's a pot, there's a hope. I methodically turned the controls through their range. Still nothing. Have I bought a doorstop? It's always the last control that does it. Of all things it was the antenna trim.
 Now I've got genuine band noise! Turning the main tuning anti-clockwise, in pops Radio Moldova. I am now a believer that hollow state sounds better than any solid state radio I have been using over the years. I never knew 'warm' sound until now. Band scanning is not this radio's forte' but I can live with it.
 Some concerns;
 The dial accuracy varies between 1 and 3kc depending on the band selected. The dial Zero adjust is maxed out. Close but no banana.
 This radio seems very quiet or is it partially deaf? It picks up rf on all bands. The calibration function works everywhere.
 I was surprised that it is so easy to tune sideband, though, upper sideband is very touchy. Lower is much easier.
 Both tuning dials have seen better days. I know there are reprints for the drum dial. The kc dial has a few cracks.
 Controls are a bit scratchy/dirty.

 So, some questions;

 What can I use to clean the pots without damaging them?
 
 Is there a simple method to evaluate the sensitivity using the calibration signal?

 What components should be replaced? As far as I can tell, this radio is unmolested.

 Is there a CD available with service information? Any good books?

 Any idea where I can get the hold down plate for the big electrolytic cap?

Thanks for your help, Roland.....
 
 

[Todd, KA1KAQ]

They are great radios, Roland. I'm currently seeking one for a client overseas. The gov't procured a lot of them, so parts availability is excellent.

W3JN can certainly steer you right with respect to the do-s and don't-s of PTO repair and calibration. He's had good success with it.

There are numerous manual sources available, ePay shows multiple hits for copies and occasionally an original will show up.

For the pots I'd suggest CaiLube from Caig, the DeOxit people. It comes in a blue can and is made specifically for controls. WD-40 will work in a pinch, but I find it needs re-application before long. If you have a 15-20 yr old can kicking around you'd probably have better luck.

Until you go through it to replace bad components, weak tubes, and do a proper alignment, it's hard to say how deaf it is. They work great when set up properly or even marginally close. If performance is noticeably numb, it needs attention.

The condenser hold down plate also holds the rectifier in place, IIRC. They are often missing as rectifiers of different height screw with how it fits and a lot of users apparently just tossed them. I've got one here that I've been hanging onto in anticipation of the set going overseas. If, by some stroke of luck it's not needed, I'd be happy to send it your way. Just don't hold your breath. 

[KM1H]

Its an excellent set but considering its age needs TLC.

I also had to redo the PTO on mine and a few others plus there are some caps that need replacing, AGC especially and the electrolytics. Then a good alignment while selecting the best tubes on hand and actually in the radio.

The alignment will take care of the USB-LSB issue as well as likely improve the overall performance.

The audio is rather restricted so you can take the low level from the rear panel and feed into a good amp.

Todd, I recently sent a R-388 and HRO-500 to Spain and he just had an Ebay LF-10 sent directly to me. A chap in Ukraine wants me to find a 51J4. So there must be pockets of interest in EU for these USA BA's.

Carl

[K5UJ]

in my opinion you got lucky this time but in the future a few things you did that I would not do, based on my experience ignorantly doing them.  First, I have never owned a 388 so it may be different.  Otherwise:

1.  Don't do anything with electricity, even with a variac until you have pulled the chassis out and looked around for plastic encased paper caps, paper wrapped caps and wax sealed paper wrapped caps.   If you find any, replace them.  Metal can caps I like to replace but that one is a matter of opinion. 

2.  "Standby" may not be what you think.  I originally thought it meant filament only.  No, it can mean everything but the audio output stage i.e. you are live with B+ ... everything except muted audio.  Why does that matter?  Read #3.

3.  If there is a vacuum rectifier in there and "standby" means no audio, bringing it up with a variac will result in the vacuum rectifier suddenly conducting at some potential; not a gradual ramp up of B+.  The rig may become unhappy with that.  You can run it with a vacuum rectifier, but bringing it up with a variac should be done with silicon diodes and a dc v. meter on the B+ so you know where to stop increasing the line voltage. 

rob

[WBear2GCR]

Standby is the B+ on the R-388.
The schematic is under the top cover, flip it up and look!

My calibrator makes about S-9 on 75m, maybe a little more.
You can tweak the first RF coils iirc... the IF coils all track, so unless someone
turned them all there is nothing to do.

I cleaned and then re-lubed all the obvious moving parts on the cams that move the slugs... I used synthetic (silicone) grease. I also use heavy silicone oil for things like the shaft bearings, after cleaning them with a spray aerosol electronic cleaner... heavy silicone oil is sold for "shock oil" at hobby shops in assorted weights... I use a syringe to apply. Never gums up.

Mine scans the band really well and fast...smooth.

I like the stock audio, but i use an Altec 12" coax speaker... high sensitivity speaker, so not much power is needed to make it pretty darn loud.

It's presently my main 75m AM receiver.

Upgrade path is to put the softrock 500kHz SDR on the IF out...

                        _-_-bear