Addendums

Updated February 4, 2021

Important!!! See #4 & #5 & #6

#1 It has come to our attention that the FET transistor, Q1, may have the wrong pinout in a batch that we purchased back in February 2018. The package dimensions, primarily the flat side is on the wrong side Thus the pinout is reversed. Most have been recalled and replaced but there may still be a few that were shipped from February to June that got by us. The symptom is the audio is very weak or non existent.

You can determine this by the following:

1) Noting the background noise with the gain turned up. You should hear a noticeable "sea shell" noise even with the antenna disconnected. Another way is to take a wire or resistor lead and short R9, the 4.7 meg resistor. If the noise level comes up much stronger (in receive), the transistor is at fault. The quick fix is to remove Q1 and put it in with the flat side opposite what the white silk screen shows. If not happy with this fix, contact Midway and we will ship you a free replacement.

2) It seems the only ones we've noticed that are packaged wrong have a code on the flat side marked F D316 just above the MPF102 part number. All other FETs shipped with different code markings should work fine. (Example: F B510, M849, 418, 438)

Care should be taken when handling and soldering these devices so static electricity doesn't damage the device. If you need this part immediately any N-Channel junction FET should work such as the 2N5457 or equivalent. Just verify the pinout, specifically the gate.


#2 It has come to our attention that since this legacy design in 1996, the FCC regulations have tightened the harmonic limits from 34 db to 44 db. The original design and what Midway has in the ME+ kits don't quite meet this new regulation. Midway has a fix that will bring the ME+ series into compliance. See Compliance Fix. Also the carrier envelope is too steep and may cause off channel chirping. A 4U7 capacitor across the base of Q3 and ground will bring this into compliance.


#3 Beta assemblers of the ME20+ kits have neglected to remove the tubular capacitors from the base of T1, T2, and T3 even though in numerous places in the manual it is stated to do so. If the transformers are installed without the removal, the ME20+ will not work. Removing the transformers from the board is not very successful without an expensive vacuum desoldering tool. The circuitboard should be sent back to Midway for this procedure. See 20 Meter Mod for more details.


#4 It has come to our attention that some 20, 40, and 80 meter kits were sent out with some wrong capacitors. The ones in question are marked 470 or 470p which are 47 pf capacitors and they were supposed to be marked 471 for 470 pf. They are used in the tank circuit in the output stage. In the 40 meter kit they are C37 and C39. In the 20 meter kit it is C38. The incorrect values will not resonate the tank circuit correctly but will not affect the receive sensitivity. In the 80 meter kits they are C1, the receive input transformer (which will cause the tuning range to be off) and C31 between the two filter transformers in the transmitter which will cause insufficient output. These kits were shipped from April to November 2018 and problem was just caught Nov 24th 2018. We are attempting to send the correct parts by mail to all kit owners. If you can't wait and have a supply of 470 pf ceramic disks, you can replace them yourself. It is recommended that you cut out the wrong capacitor and solder correct one on the bottom of board. If you happen to have a good vacuum solder station you can remove the wrong capacitor but you have the potential of removing the thru plating. Should this happen just make sure you solder the top pads too. We are sorry for the inconvenience.


#5 Recently we have had two kit builders return their kits for extensive repair due to massive destruction because of an improper power supply. It is important to note that the power source via the 2.1mm coaxial plug is a center positive voltage. In one instance the supply was center negative and got past the diode block, so he claims. In the second instance the power supply was a 2 amp AC wall wart that fried part of the circuit and detonated an electrolytic. Usually AC power supplies use a 2.5mm plug and in this case it was possible to plug a 2.5mm plug into a 2.1mm jack. Please make sure your supply has a center positive as shown on the silk screen on the back of the enclosure. Also make sure if you use a standard transformer type wall wart that its unregulated, voltage can exceed 17 volts (even though it's marked 12VDC) which may make the ME series transceivers unstable and cause hum. Later light weight wall warts are switching power supplies and are usually closer to 12 volts.


#6 As of Feb 2019 we had a few complaints that with stereo headphones, people were only getting the left channel. Looking at our supply of jacks in stock, the supplier sent 2 circuit mono jacks instead. We have pulled these from stock and kits and if you happen to have the wrong jack too, let us know and we will send a correct one to you, or you can obtain them locally. Remember, it must be a 3 circuit stereo jack. The jack for the key can be any configuration since you only need the tip and sleeve (ground).


#7 There might be a discrepancy in the gain pot value. The manual may state in the parts list on Page 19 as being 10K while the pictorial on Page 12 states 5K. Actually either value will work but the Page 12 values will be corrected in future manuals. Also the tuning pot value says either 50K or 100K (M10). Here again, either value will work but the manual will be corrected on Page 12.


#8 September 9, 2020 We've had some 20 meter kit builders experience low power output from their ME20+ kit. After some testing we have found that the driver transistor Q5 doesn't have quite the drive required to drive the output transistor. This could be just a batch of low gain transistors or it may require a change in the parts kit with a different transistor. In our tests we've substituted a 2N2222A or 2N4401 transistor and this resolved the issue. Until further testing, as of 9/9/2020 all ME20+ kits will have the 2N2222A or 2N4401 transistor shipped with the kits. Once we've determined the issue we will make the final decision as to a permanent fix. Previous ME20+ kit builders will be contacted to see if this has been an issue. Please contact us by email if you believe your 20 meter unit suffers insufficient power output. See transistor fix1 for the correct pinout information.

Update: 11/26/2020 A simple fix is to use a 2N4401 instead of the PN2222 or 2N3904. Contact Midway if you feel your output is insufficient and we will send you one.


9) Recently we've seen a number of kit builders damage the T1, T2, or T3 transformers by applying too much pressure while tuning the slugs. This will permanently damage the transformers. Please use very light pressure when tuning. Contrary to good RF practices it is okay to use a metal screwdriver to tune these transformers because of the lower frequency. Just be careful not to press too hard.