Most of the variable trimmer caps were stuck, and since the coils were so close, i didnt risk breaking anything and didnt apply force. What follows is a posting for a 75a 4 that i sold on the internet. Co 80227 948 was ihr first full year ot pmdix lion for i hi revolutionary new collins 75 a 1 receiver, advertised as the lint really new design since the introduction the superheterodyne. Ham radio enthusiasts nicknamed the pair the gold dust twins, as they were unaffordable to most amateur radio enthusiasts when first introduced. Collins pushed the state of the art with the 75a 4.
One of the main things to look for is the hardtofind 800 cycle cw mechanical filter. Click on the title below to explore more about the highlighted. Today i mated the 55g1 reproduction by dave w3st and my 51s1 which peter. Collins 75a 4 what follows is a posting for a 75a 4 that i sold on the internet. The 75a amateur line was updated throughout the early 50s, finishing with the 75a 4, which was released in 1955. One view is that the 75a 1 was simply referred to as collins 75a until the 75a 2 came out in 1950. Solid state driver amp for collins 831g2c fm broadcast transmitter 88. Collins 75a4 hf receiver documents and modifications w0ui. V201 and v202, the two 3b28 halfwave rectifiers, do not have pin identifiers. This is a 75a 4 radio we sold many years ago collins radio company first production 75a 4 receiver built. Following the directions in the manual which is very well done and published by ted.
A legacy of high quality pari 2, the 75a 1 by ray xtrrwald, n0lms 10679 wrsl dartmouth avr. The umbilical cable to the kws1 transmitter feeds in the lower right. I do have all 4 of the aline receivers, 75a 1, 75a 2, 75a 3, and 75a 4 and concur with the ratings of the receivers for am reception. Noise limiters and audio amplifiers 75a3 alignment adjustments dial cord replacement. Collins items capacitor replacement kits nationwide radio. For included in the package was the matching collins 75a 1 receiver, collins 270g 1 speaker, collins 310a exciter to the drive the big 30k 1, w7mgas manuals, extensive spare parts, a homebrew coil holder and shure microphone. If you have some stuff that not is listed here you can donate this by contact mods. Endorsement by ed, wa3bzt home of the collins radio association. It is suggested that the user of the instruction book make the changes given in this supplement in his instruction book. In recent years, the number of licensed amateurs has been increasing at an accelerated rate. The item youve selected was not added to your cart.
Hi john, i have scanned in a 75a 2 schematic and will send it to you in a separate email. When the 75a 4 was introduced, all of the then current receivers were relegated into two classes of radios. A legacy of high quality pari 2, the 75a1 by ray xtrrwald, n0lms 10679 wrsl dartmouth avr. As a glance at the schematic told me that the tube needed to be in place for the receiver to operate, my concern began to grow. Solid state direct replacement modules are much more efficient than their vacuum tube predecessors.
Collins 32s 1, 32s2, 32s3 new chassis mounted replacement capacitor can. Collins 30l 1 rf linear power amplifier service bulletins manual. Another theory suggests that a small run of 200 75a s were made in 1946. I checked the packing material, searching for the missing tube. We have 1 collins 75a 3 manual available for free pdf download.
Simplified schematic of 75a 3 rf circuits 75a 3 receiver, schematic diagram 148c 1 nbfm adaptor. To my memory the collins 75a 1 and 51j receivers were the only two in the late 1940s with a crystal controlled first conversion oscillator and precision pto. In addition to superb selectivity and stability, the 75a receiver has a. The 75a 3, or 75a 2a, if a wider filter is put in the 2nd filter position, is about the same as the 75a 2. Smeter circuit modifications as per the service bulletin sb2a dated late 1955 have been implemented. Original collins radio 32v3 transmitter sales invoice tag envelope schematic. The collins 75a 1 is a very good example where using the balun makes a considerable difference in sensitivity. Now, for ssb, the order is reversed even if a product detector has been added. In some case, dropping resistors should be used if the higher output voltages often yielded with these diodes will create an unsafe condition. With the experience gained in the design of the 75a1, collins released the 51j1 receiver, a general coverage hf set covering.
Ive included it because it went through an evaluation on the test bench and the specifications are noted. Pins 2 and 3 have no internal connections and not shown. The 75a 3 seems to sell for much less than the 75a 4 and yet, by my ears, offers much better audio and more operating flexibility. Pilot assy 1 the 75a 4 is commonly known to be the very first production ssb receiver made. Collins products at the time were considered top of the line. There is a wealth of other collins information on the cca website and much more to come. View and download collins 75a 3 instruction book online. A work of art a collins time capsule found by bruce j. Further, there are some interesting photographs of the 75a 4 from the inside. Collins 75a 2 vintage ham radio receiver w repro manual works great sn 1974. The collins 75a 4 is a high quality amateur band receiver covering the frequency ranges of. Skylab program used collins equipment to provide communication from the astronauts to earth.
Rockwell collins radio service instruction manuals schematics. In this page you find schematic, users and instructions manuals, service manuals, technical supplement, leaf leads and other good stuff. Both of those alternatives will usually work even better than the tv balun. Details about org photofact schematic collins 75a 1 344. For some reason, collins did not include a calibrator for the 75a 1, not even a socket for one like in the 75a 2, 75a 3, and 75a 4. This is a schematic diagram for the collins 75a2 receiver. Cedar rapids ia, build 19521954, 9 pictures, 6 schematics, 17 tubes, united states of america, semiconductors. Collins 75a 2, 75a 3 new chassis mounted replacement capacitor. Collins items capacitor replacement kits nationwide. Solid state 6bf5 home of the collins radio association. The rf stage v2 feeds the mixer at the carrier frequency of the incoming signal.
The af amplifier tube 6bf5 in the collins sline gets so hot, it turns dust particles into carbon and deposits a coating on the cabinet cover. Collins 75a 2 new capacitor replacement kit including chassis mount multi can. If you have a 75a1 be sure to compare the schematics to what you have. A simplified block diagram of the 75a 4 rf system is shown in figure 4 1. Collins 75a3 manual collins collectors association. It was known as the r388 and was used in multiple receiver diversity rtty installations. Collins ham radio receivers for sale in stock ebay. Figure 1block diagram of the collins 75a4 receiver.
Noise limiters and audio amplifiers 75a 3 alignment adjustments dial cord replacement. The rear panel has a bnc antenna jack and other io jacks. Image and if rejection the modern circuit design of the 75a has. It was left that way for four years until 2014 when the case was removed from the radio, packed up and sent to howard mills, w3hm in the u.
Stability and a 1 kc dial readout was outstanding for the day. Collins 75a4 new 26 piece capacitor replacement kit. The calibrator receives its operating voltages from the 75a 2 receiver power supply and is turned on when the limiter control on the 75a 2 receiver is placed in the cal position. A simplified block diagram of the 75a4 rf system is shown in figure 41. All of my collins receivers have a lds least discernible signal of under 0. Collins 75a 2 160 10m vintage ham radio receiver w xtal cal nbfm adapter. The 75a3is a dualconversion communications receiver covering all amateur bands in the range 16010 meters. May 16, 2017 the 75a 3, or 75a 2a, if a wider filter is put in the 2nd filter position, is about the same as the 75a 2. Simplified schematic of 75a3 rf circuits 75a3 receiver, schematic diagram 148c1 nbfm adaptor. Howard specialises in radio restorations including refinishing collins 75a 4 enclosures. Be prepared and able to communicate in case of emergency with the largest selection at. However, a 6au6 and a handful of parts i have several spare 100 khz crystals and that problem will have been solved.
Collins 30s 1 rf linear amplifier instruction manual. Full text of the collins 75aseries receivers a legacy. The recent war has introduced a great many people to our great hobby. The 75a3 saw the introduction of the famous collins mechanical filter. Collins 75a 4 new 26 piece capacitor replacement kit including chassis mount multi can. Instruction book collins 75a 3 instruction book 59 pages. This site helps you to save the earth from electronic waste. Front panel controls are identical to the collins psu. The purpose of this supplement is to show the changes in the 75a4 instruction book collins part number 520 5052 00 necessary to make it agree with thechanges made in the equipment for the buship modification. The output of the calibrator unit is coupled to the grid of the rf amplifier tube v 1 through the capacity between pins 3 and 4 of crystal calibrator socket e5. Iirc, the 75a 3 could be rackmounted on 19 centers.
The two frequency ranges of the variable if channel are produced in like manner. Cedar rapids ia, build 19551959, 10 pictures, 3 schematics, 21 tubes, united states of america, semiconductors. The receiver retains the timeproven features of the earlier 75a series notably, excellent image rejection through the use of double conversion, precise dial calibration and high stability provided by the permeability tuned, hermetically sealed collins vfo and the crystal controlled first injection oscillator and ideal selectivity produced by. Now my 75a 3 receiver has the optional collins nbfm adapter so i have not converted it to use a product detector. Collins 30s 1 linear power amplifier service bulletins. Early 75a and shows an image without limiter switch, in the remarks of the 75a1 he states differs from 75a in limiter switch.
Frequency bands, tuning and dial accuracy is the same as the 75a2. The 75a3 alsofeatures excellent stability, sensi tivity, and dial accuracy. It would be produced in somewhat updated versions 51j2, 51j3, 51j4 for about a decade. Collins 75a1 receiver service manual download, schematics. The stability of the collins pto and the classic collins design reliabilty go along with the excellent filtering to make the 75a 3 a great ba receiver. Of course, one can use an antenna tuner between the antenna and the receiver or it is certainly possible to make, or purchase, a balun specifically made for hf. Full text of the collins 75aseries receivers a legacy of. One problem the older collins receivers had was a frequency burble when tuning. It would be the late 50s or early 60s before anybody else would catch up with them. If you were around in 1955 when these receivers were introduced to the market, you had your choice of a great many receivers. Service manuals, schematics, eproms for electrical technicians. With the advent of undreamed numbers of amateur stations on the most popular amateur bands, it is apparent that a receiver capable of extreme selectivity. Collins 30l 1 rf linear amplifier instruction manual photocopy. One view is that the 75a 1 was simply referred to as the collins 75a until the 75a 2 came out in 1950.
All rf bands were very close, only slight adjustments necessary in the coil slugs. It is the only amateurband receiver featuring the collins mechanical filter. The collins mechanical filter was introduced to consumers in the 75a 3, and the 75a 4 was one of the first receivers marketed specifically as a single sideband receiver. Unprecedented compactness is achieved without crowding. Printed on higloss 24lb high quality acid free paper for a professional finish that wont turn yellow with age. If you want to checkout the service bulletins for the 75a 2 checkout the collins collectors association website. Collins 75a 4 vintage ham radio receiver w manual works great sn 245. Another theory suggests that a small run of less than 200 75as were made in 1946. Collins 75a4 service manual download, schematics, eeprom. With this in mind, the collins engineers designed a receiver especially for the amateur which solves the reception problems of the modern amateur better than any other receiver.
Vintage collins tube transmitter 32s 1 demonstration duration. Discussion of collins developed noise blankers for the kwm 1, 75a 4, and 75s 1 amateur receivers 6b noise blanker manual 200 dpi, pdf, 2. This particular 75a 4 until recently, was known only to be an early prototype, it wasnt until it was restored to operational condition by a retired collins field service technician that the actual identity as pilot assy 1 was discovered. A two position concentric switch under the bfo knob selects the supplied 3 khz or the optional 800 hz mechanical filter. Collins 30k1 station time capsule amateur radio station. Of course the 75a 4 had a product detector from day one. The first conversion circuit, consisting of a crystal controlled oscillator, v4 and a mixer tube, v3, converts the incoming signal to the variable if frequency of 2.
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