Sweep Tubes overheat in Antique D/A Raider Linear Amplifier
This does not match any category : D/A Raider Ham Tube Linear Amplifier . Everything looks great, but the 4 main sweep tube filaments overheat, glow abnormally bright . I do not use this amp because it will just burn up the 6LQ6 sweep tubes . I havn't made tests, but I suspect a possible short in the transformer . The filament winding, and the high voltage windings are combined in a single large transformer . I don't know how to match a transformer for this OLD unit . I was considering a seperate filament transformer . The power cord has been replaced with a modern grounded type, but that looks fine . All switches, relays, wiring, and hardware are good . The 4 main HV capisitors are new . The cooling fan has beed updated . If anyone is still living who understands tube amps, and has a clue to solve this problem your help may keep this cool antique alive . Thanks, J.
- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
If it is made by Palomar and it is a small amplifier, you can bet it is a low drive. Check those transistors. It could have the new Mosfet 655's in which case definitely low drive 3-6 watts input max.
best way is to leave the radio in piece and obtain a linear amplifier to do the job a 10 meter ham radio amplifier will do nicely but you must re-tune it for the 27 mhz band 10 meter band is 28 mhz. RF amps work best using side-band mode.
You can buy T8 led light tube by a website of foreign country.Below is the best site where can help you buy the best T8 led light tube.http://www.ervan.cn/products/L05G-I33V-Emergency-LED-tube-.htm
* ALWAYS UNPLUG YOUR AMPLIFIER BEFORE REMOVING TUBES *
If you can see that a tube is definitely not lighting up then it may be blown. If this amp has seen regular use then it may be time for a new set of tubes. Try replacing the 12AX7s first before committing to a new set of 6L6s. Though, if you have the cash available, a new set of power tubes isn't a bad idea either. I would advise you to do the preamp tubes first and play through the amp for a few days first before changing the power tubes.
Keep in mind... if a tube (or tubes) has blown, there could be another issue in the circuit. Swapping in a new tubes is a quick way to determine that. Then it would be time to take it to your local repair shop.
A high frequency feedback can be very hard to isolate without test equipment... you MIGHT have a "microphonic" tube that picks up from the speaker and feeds back... Tap the small tubes with a pencil and see if any of them "ring"... gentle taps of course... If one seems sensitive, swap like numbered ones around to see if you can find a happy place for them. Electrically there could be a bad ground inside causing these.
I notice you have 4 tubes in the output... REMEMBER when you used matched pairs... the members of the pairs do NOT go side by side all the way down the string...
Put each tube of a matched pair at the ends of the string of four, and the other pair as the middle two...
Check the bias on the tubes! Some brands can run with bias set wrong. Also some amps have 4 output tubes and people don't know that MATCHED pairs have to be seperated to each side of center of the group of four tubes.
You probably only have a single EL84 tube in your unit.
I could not find the schematic for this unit... IF the plates of the EL84 are coloring, the bias is set wrong. The plates should remain BLACK and not coloring to dull red or orange. Telling if the tubes are "burned up" can only be done with a tube checker or electronic test equipment or by seeing a bright purple glow between the elements.
Now this is supposedly only a 5 Watt unit so that means it is for LOW volume practice only... If you overdrive this small amp you can PROBABLY burn almost any tubes you put in it. The sound you can expect out of this will not be louder than most of the consumer boom boxes at full volume.
If you overdrive and "flattop" the unit the power tube will overheat and fail... this amp runs the tube in "Class A" which makes failure under overdrive more likely than in Class AB or B. I can't go into the engineering details other than to say at volumes above the design the output transformer will saturate and the tube will have to dissipate way above its ratings.
This is not a transformer problem, it would blow fuses if transformer shorts out. It is hard to say, what could cause the problem without looking at the unit. But, you mentioned new power cord with grounding. That looks suspicious to me. Tyr to diconect grouding wire, and see if that helps.
Are the tubes bad? Do they light up? Check the tubes and install replacements if necessary. If it's a preamp tube that went bad, just replace that one tube. If a power tube went bad then replace the set of power tubes. Be sure to get a matched set when replacing power tubes, and to bias them.
This sounds like a power supply problem. The high voltage for the tubes is not right. Either you are missing an amplification stage because this or one of the coupling caps is faulty. I'd have to see the unit itself to give you any more details.
×