TE & SOLID STATE AMP PAGE!
Due to lack of time and the fact that there is little money in repairs, I am NO LONGER doing repairs. I have enough of my own stuff to fix!!
2M 25W in, 350W OUT MODELS
If you have or buy one of these amps, Do this simple test before extensive use on SSB. The 2m model uses a driver (MRF-247) that is designed for around 10-15W input for max out, around 80-100W. The final stage uses 4 of the same. With this much gain, it usually does not take more than 10-15W to achieve full output. Anything more is just a highly saturated transistor and the signal begins to get very wide! Please do this simple test......connect a good wattmeter with a dummy load and see how much input it takes to get the 300+ watts out. Then, mark that spot on your drive level. Now you're ready. If it is not quite 350W, DON'T PUSH IT!!! Every SSB radio with the exception of the Kenwood TM-255/455, puts out between 15-20% more power on SSB voice peaks than it does on CW or FM. For example, My TS-711A, rated at 25W, will peak at better than 30W SSB. My IC-275H peaks at around 120W. That is using a scope for power readings into a dummy load. So....Just because it only reads 310W, It is probably more like 360-400WPEP. And yes, it does help to run the voltage up to 14.7 VDC. Following these guidelines will help clean up the bands!
LOW POWER IN, HI POWER OUT MODELS
Same setup procedures as above. Set your radio drive level to achieve rated output, NOT rated input. You will find it takes a lot less drive to run these amps than is stated.
I have seen several of the preamp relays in these things go bad. In many cases, they will stick and short 12 VDC to ground. I have seen the relays actually catch on fire an burn up the entire board! Since they will only handle about 7-8 amps before melt down, it will not blow the main fuse when this happens. The fix I do is install a 1A fuse in the circuit to the relay control so if it does short, the fuse will blow and save many components. I also remove what's left of the old relay and install a socket so the relays can be changed easily.
HARD KEY YOUR AMPS!!!!
I am a firm believer that RF keying your high power amps will shorten the life of the relays......Besides...I hate the sound of a VOX circuit. If your rig has a jack to do this, use it....if not...wait until the relay goes...then call me.....hi
DON'T BOTHER WITH THE SCHEMATIC
I have yet to find a correct TE schematic.
BEFORE YOU SPEND THE MONEY ON A 170W 432 AMP....
I strongly recommend the Teletec amps. UNFORTUNATELY...Teletec is no longer in business! They are only rated at 150W, but they are MUCH more linear and they typically do around 200W at center freq......so if you have it tuned for 432....they are as powerful as the TE's and draw less than 1/2 the current! The gain on the preamps in the Teletec amps are not as high but the insertion loss is MUCH less than the TE amps so you don't really need it. The insertion loss in a 432 TE is greater than 2db so that's why it seems like the preamps are working so good in them.
A NOTE FROM TELETEC ON PREAMPS
When people ask for a "better" device they automatically think of a GaAs FET instead of a J-FET. This is due to the gain level being greater. (12 db vs 8 db typical) There are other areas to consider than just receive gain when it comes to designing an Amp. A higher receive gain is not necessarily a good thing when it comes to an over-all circuit design.
The bottom line is, that with the AB2 circuitry that TELETEC is using, there is no sigificant difference! We have tried both! The only differnce we have been able to come up with is price. Simply put, the GaAs FET cost more. We chose to put our money into other aspects of design and components in the AMP.
The J-FET is clearly a more rugged device than a GaAs FET. It will endure more abuse and it cost less is the bottom line. TELETEC is known for making an Amp that we call "TELETEC TOUGH". At the same time, we have to be able to deliver a product that is competitive in price to other Amplifiers that are out there. If we were to build the "IDEAL AMP" it would certainly cost more than the "Typical Ham" (all of us) would be willing to pay.
Thanks Greg, for the opportunity of explaining why we chose to go with the J-FET. I will be glad to answer any of your readers questions should the need arise.
73-Bob Batten........ firstname.lastname@example.org
Sales Manager TELETEC
The entire system NF is greatly affected by the first device in the system. A high gain, low NF device will greatly improve receive capabilities. A low gain, medium NF device will do little for receive at the front of the system.
I have sucessfully installed a DEM GaAsFET preamp inside of a Teletec 432 amp and it works great! For more info, email me or in the future, I may post some instructions here. I can do it for you, but as I stated at the top of the page.....my time is limited lately.
SOME OTHER TE NOTES
All the TE amps of the same output power use the same circuit board.....yes, even the 6m board is the same as the 432 board!!! If you want a good laugh, open your 6m amp and look at the xistors and you can see where they took a dremmel tool and ground away the circuit board to make the xistors fit and where they cut it to add the coils to give it enough inductance. I believe this is why the 432 amps are only good for 170W out of almost 300W worth of xistors. Too much inductance built in to the board for the lower freq's. I built an amp using 2 of the same xistors and got 150W out of just two MRF 648's!....I guess it saves a buck or two.
Converting to Hi Power Inputs
If you have one of the low power input models, ie 1-10W in, and have a higher powered radio, It is quite easy to convert them to handle the higher power. The hi power out models will take up to 60W in on 2m, 80-100W in on 432 and the hi power 6m amp will take 25W in after the conversion. The max in on the low power out models, 110-160W, will take up to 25W on 2m, 25-45W on 432 depending what transistors they decided to use and the 6m version will only take 10W. This is true for all amps, not just TE. I have done this to both RF Concepts and Mirage amps too with the same results.
6 Meter Amp Spurs
I have found several 6M amps that do this and there is an easy cure. First, how to test it. Turn on all the radios in your shack, especially 10m and 2m, but if it is oscillating, it will show up on ALL bands up to 432! Key the amp and radio at the lowest power out, then slowly increase the power output up to full power out of the amp. If there is an oscillation problem, there will be one point somewhere between no output and full output where there seems to be a carrier on all the radios in your shack! The ones I have seen do this are somewhere around half power out of the amp. If there is nothing, congratulations! If there are spurs, check around the transistors for a feedback circuit. Most TE amps use a resistor off the collector thru a capacitor to a coil to the base of the device. Usually a 33 ohm resistor,1 or 2 watt, a "503" or.05 uF cap and about 2 turns on an 1/8" ID coil. Some other amps have a low value "swamping" resistor on the base, usually 10 ohm, and a .1uF cap with a couple of turns on each leg from the collector to ground. The TE circuit is the easiest to fix. Usually changing the value of the resistor will cure the problem. The last one I did came with 27 ohm resistors. At about 110W out, it lit up every radio in the shack while on a dummy load! I first tried reducing them to 22 ohm and the problem got worse. I then increased them to 33 ohm and the problem went completely away! I could operate the amp at almost 400W with the antenna less than 3' from my 432 and 222 antennas and not tell I was transmitting on 6m! I also quit tearing up my VCR and TV! If you have the other type, leave the resistor on the base alone. Changing this will drastically affect the bias of the amp, besides, it doesn't do much anyway. Remove the .1 cap on the collector and add an RCL circuit like described above. The inductor is a TE part and is marked LQ-157. I will say, it is very easy to get parts from TE and very inexpensive! It can also be easily made with some #22 and an 1/8" drill bit...about 2 turns will do it. The same circuit can be found on all the other amps for the other bands too. The 432 and 2m amps use lower value resistors and more turns on the coil but still use a 503 for the cap.
Why don't they detect this at the factory???? Well, you have to remember, they tune amps at maximum power and even a two tone test is done at full power and the problem does not show up except at a specific power level.