[bridkarl]

I got this SX-62 up and running today. Replaced the filter cap, some resistors. New power cord. The tubes tested good - just barely. I installed a fuse block, but decided not to hook it up and just have it wired as original. It pulls .6 amps at 112 volts with no transformer heating after 30 minutes. 

This works well, but the volume seems low. I’m currently attributing this to worn out 6v6 tubes. 
I’ve sourced an original audio transformer if needed. 
I expect also have more bad resistors to find, but at least I’ve established basic functionality and not wasting time on something with a blown transformer

[David]

Checked with the place were I buy tubes they have them in stock. This is local for me being in the same state have done business with them for many years.   https://vacuumtubesinc.com/index.php/6v6gt-6v6gta.html

[bridkarl]

Thanks. I use this guy who operates under electric guru parts house. Been buying tubes from him for years with never a problem.

At this point I’ve sourced all the missing parts - knobs, pointer adjust, the shield cover as well as a replacement stock audio transformer.

I’m planning to swap out the tubes and see what difference it makes. I’m also going to continue and replace resistors as needed

[bridkarl]

Today the volume was gone. Had done nothing but replace resistor on sensitivity control.?

I think this salvaged audio transformer the previous owner had just died.
I’ve sourced the correct audio transformer which I’m installing. Of course the colors have faded in the wiring so I’m having to make best guess as to what was originally red.

So does this happen to other people? You repair the radio correctly - undoing the bad repairs - and parts simply die like they don’t want to work anymore?

This radio does work, had low volume - replacing audio transformer and all tubes - hoping it brings it back to full volume.

[David]

Rule of thumb when I fix a radio it is not fixed until it runs for 8 to 10 hours with no new problems. David

[bridkarl]

Had to put in three new tube sockets and rewire them.

Put in just the rectifier. Got filament voltages for about 2 minutes and then nothing. No current draw. However I saw no issues like burning parts, heating transformer etc so that seems good. I got this DC hum through the speaker. 

Turns out the rectifier tube is bad. I measured about 260 vac on the tube but very low voltage on the DC.
My other spare 5U4G tubes tested bad so I’ll order a new one.

I guess this is progress.

[Chas]

I got this DC hum

 

Joke aside... Take a good look at the pin count on the sockets, be sure the connections are correct. Look closely, too, at how the solder has flowed. Certain brands of sockets are plated with a alloy that does not "wet" very well with common rosin core solder. the connection may look good but is not.. I have encountered such sockets in PC mount, the pin completely disconnected from the solder joint from heat cycling.

A LOT of small things can cause low volume, start with the bias on the output tube, too high (negative) will reduce gain, too low (more positive) will to but be accompanied with HOT output tube and reduced "B" voltages all over the set...

If the output tube is turning cherry red, it may also be ruined, as torn off cathode oxide (from high plate current) will contaminate the grid and make it an emitter.

Take and post some pix of your socket installation and solder work for criticism

Chas

[bridkarl]

I’ve replaced both 6v6 and the 6sl7 with ceramic sockets as the original tubes had broken pins. New components throughout and wiring. I’ve checked this over fairly carefully against the schematic but I feel sure I missed something.

[Chas]

In reviewing the images I see:

Extra wires in a new socket terminal that are extending far beyond the terminal. Both lead wires and component leads are also invloved. It appears that these can short or are shorted to the socket ring or wach other.

Cpnnections do not NEED to be neat. Howevr, any distubance to such socket installation could easily lead to a short, if not now, in the future as the set continues to be serviced.

The soldering to the ring of the socket is fine as long as there is toothed lock washers to bite into the chassis on top and the socket metal ring down below.  A toothed solder lug is more appropriate and would give more component spacing.

I would suggest:

That smaller better quality tools be used to form the component and wires. Four inch plier size is fine. The use of offset needle nose are much more handy and take sandpaper to break the sharp edges of new pliers so that they are less likely to nick the wire. A 4" full round nose plier is very useful to fabricate smooth, uniform bends in component wires too. There are flush cutting extended nose diagonal cutters to get between tube socket pins to snip the wire ends. Flush cut means that there is no pointed edge to the cut wire.

Better quality tools are expensive. I have specified a brand of box joint pliers (German) averaging some $60 each.. Company purchase, I had to give them up when I retired

Overall, solder flow/temperature looks good, don't change that

It is best on audio and IF circuits to leave "some" component length and form the leads with the round nose plier at the component body. The helps in grabbing the component by the lead with heatsink pliers if need be and to prevent any wire stress at the component, especially resistors.

I do note that there is a mix of capacitor types. Just a note...

The one socket has the negative of an electrolytic connected, unless that pin is also grounded or part of the bias, O.K. if not, cap may be miss-configured.

I DO think these repair sare the source of the no signal just hum. BTW hum 60 hz or 120 hz, that is a clue...

GL

Chas

[bridkarl]

If you mean the 20 mfd electrolytic that is how it’s supposed to be - it’s connected to ground. I’m replacing that with a proper 10mfd. The orange drops and carbon comp resistors were in there as found. I’ve generally used the tubular caps with no big issues but suggestions on a particular brand are welcome.

I agree on the wires. I’ve struggling along with these wire cutters that are just too big. I’ll upgrade to a better set of tools. I’ve been using these from Harbor Freight but they aren’t making the grade.
I recently upgraded to a Yihua soldering station and got a solderpullet. I’m normally soldering at 710 degrees
If you have a brand name for those German tools I’ll take a look. I see Graingers has Knipex which I think is what you mean

[Chas]

I’m normally soldering at 710 degrees

That is too hot. An iron with too little copper mass and/or wattage to hold heat has to be raised in temp to do the job. Net result for items like point to point is there is too much to heat and the scorching temp roasts the flux before it can do its job.

See if a large tip with more mass is available for that species of iron or look for an iron of both higher wattage with more tip mass. May not be able to satisfy a removable tip option.

https://www.techni-tool.com/

https://www.jensentools.com/

Though I had seen that German brand [H-K] a few years back I think they went out of business, the web cannot find them...

Any brand that either Jensen or Techni-Tool sells is good quality.

I have been using at home Utica, they once had a local distributor. If I would break a jaw, they would send it back for replacement, free. That was then

Knipex seems good quality and has box joint options. Select the bent nose pliers carefully as the length of the nose and size of your hand will determine how effective they are for point to point wiring. May want to move up to 5 or 6".

Offset, flush cutting diagonals are the best for managing cuts on both circuit boards and inside cramped chassis.

I discovered certain pliers/cutters are my favorites over time, others I have, well, suck. Like screw drivers, I have a drawer full of them, most, the bits ,have been ground or stoned to fit a certain slot...

I used to "stone" my diagonals when at work. For the lap joint pliers, in time the joint loosens, I'll bash the joint with a ball hammer to tighten it up...

GL

Chas

[bridkarl]

I can easily lower the heat. I’ll put it back to around 375. I’ve been using this Kester “44” 60/40 solder and that’s the recommended temp. I’ve been using a pointed tip but it’s swappable for a larger angled tip which I have.

Previously I was just using this 40 watt WLC100 Weller with no temperature indicator. I think I was routinely using it at the max which I realize now was wrong.


Thanks. This is all a learning process. Although last week I was watching the tv Show FBI - the terrorist was soldering up their device - I recognized my Weller as the soldering iron they were using - truly I am a radio nerd.

[bridkarl]

I picked up these. Certainly better than Harbor Freight    

[Chas]

Take a look at this:

https://nepp.nasa.gov/docuploads/06AA01B...8739.3.pdf

Though oriented towards PC/surface mount there are termination drawings applicable to terminals that could be point to point...

Note the "strain relief" bending techniques for components...

The 60/40 has a longer "plastic" state meaning that it takes somewhat more heat to melt and stays "chewy" longer than 63/37.

When repairing an old joint the eutectic alloy 63/37 is a better choice as it will amalgamated with the old joint and lower its melt point, further than 60/40 meaning flow new 63/37 on old joint then suck out all. When ever any solder alloy is used in a joint it alloys with the base metals and raises the melt point. Fine for new work but when returning to the same joint it will need a higher temp to flow or apply the eutectic solder first..

The notes are in text as to "clean as you go" using rosin solvents.

May also consider either a magnifying visor or a few power lighted glass on a crane for the work bench.

Bench also needs LOTS of lighting to see the details and the wire "hairs" that often happen with stranded wire.. Stronger lighting makes the iris in the eye close more, we will get a greater depth of field so objects over a range in depth will be in focus. Makes "Boo boos", much more noticeable... The new LED lights are great as have adjustable color and brightness without the heat. I had all quartz lamps on my eLab bench at work 30 ya, roasting!...

Chas

[bridkarl]

Thanks. I have one of those new led lights with a magnifier which I will be using to check this. I tend to use solid wire rather than stranded - just to avoid these issues with loose strands of wire when using stranded wire. It’s also why in part I chose to use new sockets so that these were new connections instead of being done over old ones. I’ll take a look and see if I have any of this 63/37 solder. I have probably a half dozen of different types in my shop. That’s something I didn’t know - thanks