They just did not handle the AC power switching function well, and often failed. Otherwise I had a lot of fun with mine. You outgrew the DX60 once you upgraded. Transformers, capacitors, EM tube all good. Another important value of feedback is the considerably improved regulation of the output, which is useful when the mod- ulator is used to drive a class B load. Yes, you can use a transformer to reduce the impedance for your speaker or headphones, but In the latter service, the gain con- trol R4 is set to minimum and the second stage behaves as a grounded grid amplifier.

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Rest the modulator on either short side and remove the bottom plate. An item that has been previously used. The did not make you a big gun on AM, but you had to go to an amp or big iron surplus to get more worthwhile real S units.

The circuit is nearly identical to many tube hi-fi amps of the early s, except smaller coupling caps were used and a clipper filter stage was included. Add to Watch list. To attenuate power- wasting low frequencies outside the modulatir range, the coupling capacitor C2 is low -valued.

Potentiometer R29 controls the 7330 volt- age. Set AC switch to OFF and disconnect modula- tor from the transmitter and any remote switching relay remove plug from octal socket J5. Over-modulation is evidenced by clipping which occurs when the peak value of the audio modulatir signal from the modulator exceeds the plate voltage of the RF amplifier.


Check the adjustment by speaking in- to the microphone quite loudly; loud speech should not be able to cause over. Learn more – opens in a new window or tab. The most important thing is how it looks on a scope with a sine or square wave generator.

AC Switch; Connects or disconnects unit from a-c line. The rewiring procedure is as fol- lows: Back to home page.

Eico 730 modulator/ driver

Overlapping of the green indicating bars occurs when the output audio signal exceeds the plate voltage of the RFamplifier stage being modulated over-modulation. I have performed mods on a and it sounds great. It used commonly available 6CA7 hi-fi tubes used in the great Dynakit Stereo 70 amplifier.

Clipping gets a lot of bad press due to bad design of some rigs, and the over use of clipping by meter-benders. If necessary, replacements can be obtained directly from EICO. To do this, it will be necessary to modulatir the bottom plate and connect the black-green lead V power transformer primary tap to the AC switch terminal Sl-1 instead of the black-red lead V primary tap.

Modulatog V7 filament not lit. The use of feedback greatly reduces distortion and ex- tends the range of uniform frequency response, resulting in increased clarity and pleasantness of speech.

Eico modulator manual/schematic?

Another possability would be to make a simple diode detector and listen with headphones. The operation of the remote control relay in conjunction with the modulator remote switching eicp from pin 8 of the octal plug and ground is as follows: The transmitter ground binding post should be connected to a true earth ground.


When the relay is energized at the transmit function of the transmitterthe relay contacts used for remote switching are closed and thereby the center-tap is grounded, causing the modulator plate supply to oper- ate. They even had a surprisingly affordable tri band model sideband rig covering the most popular bands 80, 40, 20 during the early days of SSB, but it drifted a lot. The Model should not be operated wi thout modulatr proper load under signal conditions, as the high voltages moddulator ated in the modulation transformer may damage it.

Eico modulator needs tubes. Transformers, capacitors, EM tube all good | eBay

Bypass the clipper filter stage. The Model provides low level speech dipping and filtering with peak speech fre- quency range circuitry.

Learn more modulaotr opens in a new window or tab Postage: Break the circuit on the cold side of C3 and the output side of L1. Their best offering is the Eico If you want to do two changes, do numbers 1 and 2.