[trentrosa]

So I pulled an old record player (cabinet with player, amp, and speakers) out of an old granary (I live on a farm) and took a look. We started it up and the turntable works fine, you can hear the recording playing ever so slightly from it , however the speakers wouldn't make sound, so we trouble-shooted the amplifier (the speaker compartment and speakers appear to be in excellent condition, clean and like new). After examining this ancient amp, I looked at the larger tubes (output tubes?) and 2 of 3 appeared to be burnt so I am assuming that is my issue. The model of these tubes is General Electric 6V6 GT. I found some on ebay, however I am wondering if I can replace them with different, newer models for a better sound. As with the smaller tubes (input? 2 for record player and 2 for tape input? -  total 4) These are General Electric12AT7 tubes. I have no idea if or how tubes need to match up (are these special tubes?) so maybe give me some suggestions.
 
If you refer to the pictures I also have some more questions:
 
a) There is that blackened ring of wire that is mounted on some board seperate from the amp, but connected via 2 green wires and what it looks like, grounded by a small wire simply soldered onto the amp housing. Is this a radio antenna? If not what, and does it need to be replaced?
 
b) There is that selector knob however I've no clue what the selections mean minus tape.
 
 
Well that is about it, nice little find but project it is Gotta love those giant capacitors!
 
 




 

 

 

 

 

[trentrosa]

I will also ask: is it beneficial to replace the capacitors?
 
Am currently working at pulling it out of the cabinet to allow for closer examination.

 

[duncan1]

The flat looking wound wire with one side black is the internal aerial originally glued as shown in your photo. You do not say if the amp is mono or stereo- IE- each  6V6G is in "push -pull" or they are separate tubes each with its own output transformer-are there more than one output transformer? The markings on the panel switch are FLAT =level frequency response- an input not needing "equalized" -RIAA= input for the record deck output[from the cart] old 78 means equalized for correct reproduction of 78 records- tape is for a tape recorder input the last two I don't know. Mallory caps were a good make at the time some will say change them but they can be "reformed" by passing  a  current through them and slowly raising it over time  but the3y might just be okay if you left it on before you change anything to let them "reform" as they are a good make.
                  When it comes to "trying" other types of tubes in place of the 6V6s -6L6 is near but requires a higher current. Its all very well plugging  in various tubes in head-phone amps   
                      to hear how they "sound" You wont get away with this in a tube amp with output transformers -DESIGNED and having the correct IMPEDANCE match for those particular tubes. The
                           output wont be the same and you could end up burning up the transformers[shorted turns]  . If you have two speakers REAL stereo it sounds like one half of the 12AT7 is used   
                              for each to drive each 6V6  instead of a "phase splitter"" so you should have--3---transformers -1=the mains   transformer 2 +3 =output transformers.

 

[trentrosa]

I believe its mono. Seems too old to be stereo anyway

 

[duncan1]

In that case just two transformers -mains and output-. If you have no means of testing the tubes then replace them with NOS replacements if possible get them matched[gain wise] replace the 12AT7- there are only two more choices 12AU7/12AX7 or ECC81/ECC82/ECC83 personally I would stick with the 12AT7 as the circuit is optimized for that one  6V6G are very reliable used in millions of tube radios and just lose emission over a long period -output in PUSH PULL at 285V -plate- -19V grid is approx 14Watts -remember this depends on the PLATE voltage and can vary.

 

[trentrosa]

After doing some tests I discovered the tubes cannot be burnt and the speakers work. When the record is playing and the volume is cranked to the max, faint but noticeable sound escapes the speakers. Any idea why it won't work functionally but only faintly? Also what does the tuner and aerial do? Is there a radio in this thing when you switch to BC FFR or BC STD? Or possibly, does the tuner eq the sound. The tuner knob is attached to a string that slides a bar across the display over the numbers and instrument names presented on the front shown in the one picture. It also turns a wheel that inverts slits of metal meshed between each other at the same time. The string is broken but I reached in and played with strings and the wheel. When turned, the wheel doesn't change the sound from the record player. 
 
Anyways why won't it play any louder?
(All tubes glow, but could some be performing poorly?)
 
Here's a picture of that tuner device:
 

 

[trentrosa]

bump :/

 

[duncan1]

Yes you should hear radio signals -amplitude modulation [AM] I doubt its FM-frequency modulation going by the capacitor[not enough sections] and when you turn the wheel that the tuning cord revolves on you should hear different stations. Do NOT turn it using the vanes  of the variable -air spaced capacitor as that will detune it. The mode switch has to be in the radio position which will be one of the two BC positions -use BC-STD-which should be the full AM band which is the same in all countries of the world --usually 550KHZ to 1.6MHZ. That you can hear it very faintly means the AF stage --UP TO THE OUTPUT STAGE TUBES is okay.. Tubes can light up but have low emission I have changed 1000s over the years in old tube equipment. The power supply again up to the 6V6s must be okay . So that leaves you with- low emission tubes -output transformer has shorted turns -the power supply to the output transformer -sometimes via a plate resistor [which can burn out as they are large carbon rubbish [changed more of them than I can remember]. Its unlikely that the output connections from the output transformer to the output sockets for the speakers is damaged. So check the connectors you are using to connect the output to the speakers. A quick simple test is to connect a low voltage battery across the speaker leads to see if you hear a click or thump unless you know the speakers are okay . Make sure the speaker sockets on the back of the amp/radio are not corroded. If none of the above are faulty then that leaves the mode switch they can definitely corrode with a deposit on the connectors that has to be rubbed off or if you move the switch back and forward many times it might clear enough for it to work. I know I am telling you a lot to check but that is how I would  go about it IF I WAS IN YOUR PLACE WITH LITTLE KNOWLEDGE TO REPAIR IT and NO test equipment. It looks like you have 2 wavebands or bandspread going by the photo but keep it on BC-STD. If the internal antenna has a broken wire to the coil that's come off you will be lucky if you hear any signals I don't want to tell you to touch the RF section parts  as your finger can work as an antenna as you might touch a high voltage wire but if the antenna is disconnected by one wire then use a screw. driver to touch any broken antenna parts that can sometimes be enough to make it work. Get back if you need more help. May I add BC-STANDARD could translate as broadcast-standard and MAYBE BC FFR COULD be BROADCAST -full frequency    range although that is up for question.

 

[trentrosa]

I believe my best bet is to order some new output tubes (2 6V6 GTs). As far as checking the rest, hell I have tried to pull that amp out of that enclosure but it is secured in dozens of places and I cannot disconnect it from the front panel, which is built against the wood on the opposite side.
 
Attempting to get radio through the speakers was unsuccessful.
 
 
Thanks for all the help Duncan! I greatly appreciate it. (I'm no professional at this, only 16 years old)

 

[duncan1]

You are doing the right way to go about it for someone in your situation. Forget about the RF side and concentrate on the AF side. Why?-- Its all very well saying "you have got to go by the book" -well--yes IF you have a RF/AF signal generator . -a scope- an IF bandwidth adjustment generator -an AF watt meter-a tube tester and a  whole host of other test equipment. THEN you can start at the RF end and work your way through the circuit. BUT if you cant? -then remove as much as possible of the circuit by  cutting out out the RF/IF stages and going straight to the AF . If you get the AF section working in 30 % of the cases the RF signal will then be heard if you dont get the AF working there is no point in trying to fix the RF.. Its occurred to me that the antenna  that has become detached might be used as a RF COIL and might have to reconnected to work. This was a "saving money exercise" in the distant past.

 

[duncan1]

I have been trying to find a circuit diagram for it so far no luck as the name at the back is not the maker of the radio but the retailer. BUT surprise- surprise- The company --The T. Eaton.co was once one of the largest dept. store retailers in N. America-based in Toronto est.-1884 it mail ordered for a fixed cash sum  a variety of consumables to reach PIONEER FARM communities in Canada This companies items are now very collectible as the company went into liquidation    -see E-Bay-- so even if you don't get it working -DONT bin it maybe could sell it to a Canadian Museum .