TRAM D-201(HAND WIRED)LOUD HUM?

[SIX-SHOOTER]

I have a LOUD hum in the receive on my TRAM D-201(hand wired)but ONLY on receive? Anyone know if it's a cap or what? Transmit audio is GOOD without the hum & when the radio is keyed it goes away so I don't hear it but returns as soon as the microphone is unkeyed? I am also looking for an ORIGINAL owners manual for this rig if anyone has one they no longer need or want or knows where I can buy one!

Thanks & God bless,
SIX-SHOOTER

 

[TonyV225]

Filter Caps in the power supply section will cause a hum when there bad or going bad Microphones may cause this aswell.

 

[Shockwave]

The silver can capacitor mounted on top of the chassis towards the left side is almost certainly your problem. As I recall this is a 3 section capacitor. Usually one of the 3 caps goes bad. Sometimes more. An easy fix is to buy a 100 mfd 450 volt cap and tag it in under the original. Ground the negative side and connect to positive side to one of the 3 terminals on the bottom of the old cap. When you are on the right pin the hum should go away. BEWARE, this cap will charge to around 400 volts. It will remain charged after you disconnect it and is a serious shock hazard!!! To discharge the cap short the two wires together without touching them.

You should also know you have one of the finest CB radios ever built. This is a true collectors item. Indeed radios have progressed in technology quite a bit since 1974. The fact is no other CB radio had more man hours invested in building each one. Features like a 6L6 modulating another 6L6, VFO, and VOX were quite advanced then and still remain impressive.

I once had a customer pay me a grand to make an original Tram into a 140 watt PEP plate modulated radio. The audio tube and RF tube were replaced with 6146B tubes with screen voltage regulation supplied by 0B2 tubes. The modulation transformer and power supply transformer were replaced so the plates could run around 700 volts. Variable drive was also installed. The 40 channel board out of a D-201A was installed to replace the 23 channel board because it plugs right in.

On initial power up with a variac everything seemed normal. Until I flipped the mode switch to SSB and the extra voltage arced out the switch! Hours later I had a replacement switch wafer installed with a relay to switch the modulation transformer in line for AM. It was a tremendous amount of work however it came out exceptionally clean and is still working 10 years later.

 

[TonyV225]

That thing had to be an audio beast!!!

 

[SIX-SHOOTER]

TRAM D-201(Hand Wired)

THANKS for the replies guys.I'm AWARE of what I have & am VERY "BLESSED" to have it though it has a few issues.I have ordered the TWO crystals (16.3115 & 16.5615)that had been removed by someone before I became the owner.I want it back to ORIGINAL condition so that will require the HIGH POWER/LOW POWER switch to be removed from the CAL light hole & the CAL light returned when I find one.The face & wood are EXCELLENT so that is NOT an issue either.The manual tuning knob is out of adjustment by about 4 channels(LOW)so it needs adjusting more than the adjustment screw on the manual tuner can adjust but I don't think it will be that difficult a fix.I had one of these as a young man & sold it to a local friend about 25 or more years ago & just found this one while selling some items from a SK estate & decided I wanted it for myself & made it happen when I sold another pirce of gear for the funds.I'm looking forward to getting her back to ORIGINAL condition "ASAP" & using her EVERY DAY like she was built for & I know she will do me "PROUD"! I LOVE that "BIG" TRAM AUDIO.It's like NON OTHER for sure! If I had a HAM RADIO this BIG on my desk I would have an ICOM 7700 or 7800 & that is NOT ever going to happen in my ifetime so I'll just settle for the BIG DOG of CB RADIOS & "BE HAPPY" with what GOD has blessed me with! It's so SWEET!!!!!!!

73 & God bless,
SIX-SHOOTER