Philips B3G63A

[MotorBikeLes]

I have been asked to look at a Philips B3G63A, which I gather dates from about 1957. I have fixed plenty of stuff over the years (colour TVs galore) but the only older stuff I worked on often was Telequipment scopes from the early '60s about 35 years ago. This seems to be a generation older to my eyes, so maybe needs a different approach. From what I gather here, I must replace “That Cap” which I guess is C60 A/C the Trader Sheet. But I see quite a few old black Hunts caps which I expect to be very leaky. (They remind me of the Radiomobile power section out of my Healy 50 years ago - replacing those fixed it.) Probably the cathode bias cap (C65) and the smoothers (C62 and C64) will need checking.
Anything else particularly?
Les

[Ambientnoise]

I have done a couple over the last few years. They both needed only the 6 or so black pitch Philips caps and the main smoothers replacing. The two EF80's need to be up to scratch. They sounded good, I am sorry I passed them on.

Rgds

Ken

[boxdoctor]

Due to the odd tone control circuit used in this set, there are two "That cap"s which have to be replaced. they both connect from the triode anode circuit to the volume and tone controls, and are Phiips black tar dipped types. C59 & C60 on the 'Trader' sheet. The FM section can be much improved by simply replacing the EF80s with EF183s or EF184s which are frame grid valves with much more gain.
As has been said, a really nice performer, both sensitive (on AM at least), and good tone.
Mine still needs a back cover. (Anyone got a spare one?) Tony

[MotorBikeLes]

Well, with the odd few minutes here and there, I have progressed somewhat, but now come to a temporary halt.
I replaced the two "That caps", the EL84 cathode bias electrolytic and the discriminator cap. (None checked prior, but replaced as precaution. The two black Hunts "That caps" measured OK in fact, but a couple of liquorice allsorts went in in their place.
I started with a series 40W bulb, but only got about 40v at C64 with a little less at C62. R34 O/C so replaced with an NOS one from my Grundig box. I had a 2-1/2" temporary L/S attached which now gave some weak tunable sound. After the 40W, then 60W, then direct mains, but the HT never rose above about 100v, so I replaced the EZ80 with a new one from stock.
HT volts OK now. Sound somewhat nearer to acceptable with the 15 ohm small L/S.
Playing about with the tuning knobs, FM would not travel full span. Looking inside VHF tuning box, the gang could not close because of obvious misalignment of drum on tuner shaft. Very tight grub screw but it eventually came loose, and scale set "about right". It only tunes to about 100, so classic FM (101.9MHz) and my local Manx Radio (103.75) are out of band. Maybe they could be pulled in with loss of stuff at the other end. Must consult owner about that.
I swopped the two EF80s for EF184s, but no difference in O/P, so I decided to put it back in cabinet.
Back on, plugged in, no sound. Quite dead!
I put my 2-1/2" L/S leads into EXT LS sockets, and sound returned.
So, now stuck with dead L/S.
I scraped the twisted copper leads at the point where they appeared thro the cone, but one was O/C to the solder tag. That should be fixable, but unfortunately there was no circuit thro the speaker coil. It is a 5 ohm, 6-1/2" diameter approx round one, without fixing screw holes. It has a sound cone.
Do I just "bodge something in", or does anybody have a good spare one, or even repair them. I really could not be a****d to attempt to repair it myself, too many other more important ('bike) things to do. Advice please.
Les.

[paulsherwin]

6.5” speakers are a pretty standard size so a forum member may have a spare if you ask in the right place here. The impedence isn't critical and a 3 ohm one will be fine. You could probably fit a 6" 4 ohm car stereo speaker if you can't find anything better, though it won't look in period of course. Your local scrapper / dismantler will have loads of these.

Can't you just resolder the wire to the tag?

[MotorBikeLes]

Paul, I wanted to try that. I could probably have fixed the first identified break, but scraping both wires on the concave side of cone, before entering the coil, there was no continuity. Somebody with loads of time and patience could possibly sort it, but it is a freebie job for our local post office lady.
I will look at any possible alternatives, may post here, or will try Ebay. I assume I will pass on any cash outlay costs.
Les.

[Paul Stenning]

Post a request in the Wanted section here and see if anyone can help. It sounds like the sort of thing someone would have and be able to send you. These sets are still fairly common so you might even get the exact same type.

[MotorBikeLes]

One step forward, one back. My pal turned up with a 6" speaker in a modern Philips "HiFi" cabinet. All glued up, so got in with hammer and big screwdriver. The OE L/S is 5 ohm, this is 8 ohm, 2w according to the writing. We fitted this in the cabinet and switched on, only to be greeted by motor boating. Most consistent on FM, and so I put the Selectest on the rectifier valve and saw between 5 and 10v variation at around 235v, in sync with the sound.
Early on, before I replaced the rectifier (EZ80), I hung a 50UFd (450v) cap on one section of the existing block, but no increase in voltage which was around the 100v level. Did this absolve the capacitors, or was the output low emission limited so much as to make that check valueless?
Obviously I can try again, but wondered if anybody cared to comment.
Should I be looking elsewhere for the cause of motorboating?
Les.

[Boater Sam]

Motorboating, low frequency instability, but can triggered by IF instability.
Usual causes are grid decoupling caps losing value, grid resistors from HT going high or even O/C .
Volume or tone pots going O/C too, leaves the audio stages open input.

Is the HT correct? If it is fluctuating then the output stage is drawing a heavy current as it winds up and goes bop. Check the smoothing resistor is not high and reservoir cap not low capacitance.

[paulsherwin]

Take out all the valves except the rectifier. Measure the HT voltage. If it is now steady then the problem is probably elsewhere.

Put all the valves back except the output valve. Check the voltage again. If OK, concentrate on the output stage.

It's very odd that changing a speaker has caused this fault, and it suggests that you disturbed or miswired something. Philips sets often use the output transformer to generate negative feedback, and if you miswire this it can generate instability.

[Edward Huggins]

I'm sure that replacement speaker will be rated at more than 2 watts given its a 6" unit. The only downside of adding an 8 ohm loudspeaker to a 5 ohm OPT secondary is that it will slightly reduce volume, but you may not really notice it. Edward