Another theory suggests that a small run of 200 75a s were made in 1946. 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. Details about org photofact schematic collins 75a 1 344. Figure 1block diagram of the collins 75a4 receiver. 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. Stability and a 1 kc dial readout was outstanding for the day. Collins 30l 1 rf linear amplifier instruction manual photocopy. Early 75a and shows an image without limiter switch, in the remarks of the 75a1 he states differs from 75a in limiter switch. One view is that the 75a1 was simply referred to as collins 75a until the 75a 2 came out in 1950. The collins 75a 1 is a very good example where using the balun makes a considerable difference in sensitivity. A legacy of high quality pari 2, the 75a1 by ray xtrrwald, n0lms 10679 wrsl dartmouth avr.
Collins items capacitor replacement kits nationwide radio. If you were around in 1955 when these receivers were introduced to the market, you had your choice of a great many receivers. A simplified block diagram of the 75a 4 rf system is shown in figure 4 1. Collins 75a 2, 75a 3 new chassis mounted replacement capacitor. 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. The two frequency ranges of the variable if channel are produced in like manner. Collins 75a4 service manual download, schematics, eeprom. It is suggested that the user of the instruction book make the changes given in this supplement in his instruction book. Skylab program used collins equipment to provide communication from the astronauts to earth. There is a wealth of other collins information on the cca website and much more to come. 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.
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. Service manuals, schematics, eproms for electrical technicians. 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. Noise limiters and audio amplifiers 75a 3 alignment adjustments dial cord replacement. Pins 2 and 3 have no internal connections and not shown. Collins 30s 1 rf linear amplifier instruction manual. It would be the late 50s or early 60s before anybody else would catch up with them. Cedar rapids ia, build 19551959, 10 pictures, 3 schematics, 21 tubes, united states of america, semiconductors. A two position concentric switch under the bfo knob selects the supplied 3 khz or the optional 800 hz mechanical filter. View and download collins 75a 3 instruction book online. Collins pushed the state of the art with the 75a 4.
In addition to superb selectivity and stability, the 75a receiver has a. Simplified schematic of 75a3 rf circuits 75a3 receiver, schematic diagram 148c1 nbfm adaptor. I checked the packing material, searching for the missing tube. 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. In this page you find schematic, users and instructions manuals, service manuals, technical supplement, leaf leads and other good stuff. 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. 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.
This is a schematic diagram for the collins 75a2 receiver. Image and if rejection the modern circuit design of the 75a has. In recent years, the number of licensed amateurs has been increasing at an accelerated rate. Collins 75a1 receiver service manual download, schematics. V201 and v202, the two 3b28 halfwave rectifiers, do not have pin identifiers. One of the main things to look for is the hardtofind 800 cycle cw mechanical filter. Vintage collins tube transmitter 32s 1 demonstration duration.
Cedar rapids ia, build 19521954, 9 pictures, 6 schematics, 17 tubes, united states of america, semiconductors. Collins 30l 1 rf linear power amplifier service bulletins manual. Collins 75a 2 new capacitor replacement kit including chassis mount multi can. 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. This site helps you to save the earth from electronic waste.
The recent war has introduced a great many people to our great hobby. Collins 75a3 manual collins collectors association. Collins ham radio receivers for sale in stock ebay. Pilot assy 1 the 75a 4 is commonly known to be the very first production ssb receiver made. Printed on higloss 24lb high quality acid free paper for a professional finish that wont turn yellow with age. Hi john, i have scanned in a 75a 2 schematic and will send it to you in a separate email. One problem the older collins receivers had was a frequency burble when tuning. 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. Click on the title below to explore more about the highlighted. Collins 75a2 reciever schematic diagram bigschematics. 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. Collins 30k1 station time capsule amateur radio station. Front panel controls are identical to the collins psu. Unprecedented compactness is achieved without crowding.
Following the directions in the manual which is very well done and published by ted. This is a 75a 4 radio we sold many years ago collins radio company first production 75a 4 receiver built. The rear panel has a bnc antenna jack and other io jacks. Noise limiters and audio amplifiers 75a3 alignment adjustments dial cord replacement. Howard specialises in radio restorations including refinishing collins 75a 4 enclosures. Collins 32s 1, 32s2, 32s3 new chassis mounted replacement capacitor can. Another theory suggests that a small run of less than 200 75as were made in 1946. 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. If you have some stuff that not is listed here you can donate this by contact mods. One view is that the 75a 1 was simply referred to as the collins 75a until the 75a 2 came out in 1950.
All of my collins receivers have a lds least discernible signal of under 0. It was known as the r388 and was used in multiple receiver diversity rtty installations. With the experience gained in the design of the 75a1, collins released the 51j1 receiver, a general coverage hf set covering. Ham radio enthusiasts nicknamed the pair the gold dust twins, as they were unaffordable to most amateur radio enthusiasts when first introduced. In some case, dropping resistors should be used if the higher output voltages often yielded with these diodes will create an unsafe condition. A legacy of high quality pari 2, the 75a 1 by ray xtrrwald, n0lms 10679 wrsl dartmouth avr. However, a 6au6 and a handful of parts i have several spare 100 khz crystals and that problem will have been solved. Today i mated the 55g1 reproduction by dave w3st and my 51s1 which peter. The umbilical cable to the kws1 transmitter feeds in the lower right. Early 75a and shows an image without limiter switch, in the remarks of the 75a 1 he states differs from 75a in limiter switch. The 75a amateur line was updated throughout the early 50s, finishing with the 75a 4, which was released in 1955.
It would be produced in somewhat updated versions 51j2, 51j3, 51j4 for about a decade. The item youve selected was not added to your cart. Collins 30s 1 linear power amplifier service bulletins. Collins 75a 4 what follows is a posting for a 75a 4 that i sold on the internet.
Collins 75a 4 new 26 piece capacitor replacement kit including chassis mount multi can. Original collins radio 32v3 transmitter sales invoice tag envelope schematic. The collins 75a 4 is a high quality amateur band receiver covering the frequency ranges of. 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. Further, there are some interesting photographs of the 75a 4 from the inside. Endorsement by ed, wa3bzt home of the collins radio association. Frequency bands, tuning and dial accuracy is the same as the 75a2. Solid state direct replacement modules are much more efficient than their vacuum tube predecessors. Collins products at the time were considered top of the line. 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. We have 1 collins 75a 3 manual available for free pdf download. 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. All rf bands were very close, only slight adjustments necessary in the coil slugs.
Collins 75a4 new 26 piece capacitor replacement kit. Collins 75a 2 160 10m vintage ham radio receiver w xtal cal nbfm adapter. Instruction book collins 75a 3 instruction book 59 pages. A simplified block diagram of the 75a4 rf system is shown in figure 41. 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.
Collins 75a 2 vintage ham radio receiver w repro manual works great sn 1974. When the 75a 4 was introduced, all of the then current receivers were relegated into two classes of radios. Solid state 6bf5 home of the collins radio association. The 75a3 saw the introduction of the famous collins mechanical filter. 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. Simplified schematic of 75a 3 rf circuits 75a 3 receiver, schematic diagram 148c 1 nbfm adaptor. If you have a 75a1 be sure to compare the schematics to what you have. One view is that the 75a 1 was simply referred to as collins 75a until the 75a 2 came out in 1950. 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. Of course the 75a 4 had a product detector from day one. Smeter circuit modifications as per the service bulletin sb2a dated late 1955 have been implemented. Collins 75a 4 vintage ham radio receiver w manual works great sn 245. Now, for ssb, the order is reversed even if a product detector has been added. Ive included it because it went through an evaluation on the test bench and the specifications are noted.
The rf stage v2 feeds the mixer at the carrier frequency of the incoming signal. The 75a3is a dualconversion communications receiver covering all amateur bands in the range 16010 meters. 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. Most of the variable trimmer caps were stuck, and since the coils were so close, i didnt risk breaking anything and didnt apply force. Collins items capacitor replacement kits nationwide. Collins 75a4 hf receiver documents and modifications w0ui. 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. What follows is a posting for a 75a 4 that i sold on the internet.
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. Full text of the collins 75aseries receivers a legacy. The 75a3 alsofeatures excellent stability, sensi tivity, and dial accuracy. Now my 75a 3 receiver has the optional collins nbfm adapter so i have not converted it to use a product detector. Full text of the collins 75aseries receivers a legacy of. Rockwell collins radio service instruction manuals schematics. Solid state driver amp for collins 831g2c fm broadcast transmitter 88. Both of those alternatives will usually work even better than the tv balun. Be prepared and able to communicate in case of emergency with the largest selection at. If you want to checkout the service bulletins for the 75a 2 checkout the collins collectors association website.1148 1261 333 909 532 1333 343 610 1051 1471 58 307 551 1546 27 1612 1516 553 1438 1136 792 1552 221 1339 1468 721 640 767 655 1486 1529 12 1461 1472 864 1434 1479 1446 885 1027 172 539