THE HALLICRAFTERS SR-2000

Chapter 1. HISTORY

A. Introduction

This manual is intended for those who possess, aspire to, or simply have an interest in the Hallicrafters SR-2000. We have been intensely interested in the SR-2000 since before it received its first serial number on April, 29 1966. It is unique in that it is the only commercially produced desktop transceiver to be capable of 2000 watts, the maximum legal power, not only in 1966, but to this date. We have a significant investment in time and effort accumulating personal correspondence, documentation, inter office memos, and engineering change and design notes regarding the SR-2000.

This project is in its fifth year and in that time we had hoped to revisit at least one of the engineers who designed the radio with no success. Best I can remember after 50 years, the following list are many of the folks who made these radios come to life.

R (Bob) Orwin was the project (Chief) engineer and R. Stanford the the principal designer for the SR-2000 with T Krause the project manager and R Bellio the engineer model shop for the P2000.

Seems like a hundred names surface but two others Dave Dickson and Porter Schultz had a great deal to do with the design of the SR-400 and SR-400A. The SR-400 series Cyclone I, II, and III which is the SR-400A have a long and very interesting story of their own. It will be added as I find time to write the details. The decisions that were made and the conflicts that they faced were a great story in and of themselves. I'll add the story here over time.

We have yet to find a service manual for the SR-2000 but we do have the original specifications document for the SR-2000 which is available for download from BAMA.

That said, this manual is written in a way that anyone who has a fairly good grasp of electronics theory and practices will be able to fully understand the design intimacies, strengths, and weaknesses of the SR-2000. Further, it will explain the steps and reasons needed to bring the radio to the most current production level and then review the post production changes that are necessary to correct the problems that were not addressed before production ceased. Please understand that the ‘C’ level (Most current) SR-2000 when operating to specifications is a superb radio even in a contest environment. With the additional changes provided in the follow on pages, the radio displays reduced noise level, enhanced dynamic characteristics, an impressive MDS figure, and the ability to use and neutralize 3 of 4 8122 finals rather than 1.5 of 4. The SR-2000 is notably in a class of amplifier that include the most stable and easy to use in the marketplace.

We are confident that the mysteries and myths surrounding the SR-2000 will be fully addressed over time.

B. Milestones

Before we go technical, let’s explore the information that we gathered regarding the progression of events and some of the people who were instrumental in bringing that magnificent instrument to the Amateur radio world.

We have no definite information regarding the date the SR-2000 idea was born or when the first prototype was finished in the model shop but do know that the P-2000 power supply received it’s serial number (752000) on December,30 1965 and the SR-2000, (452000) on April, 28 1966, four months later.

Early in 1966 first production models were made available for evaluation. Serious problems surfaced immediately. The final amplifier design was fairly mature in other vendors amplifiers and the SR-2000 was designed much the same. What the Hal folks did not know is one of the other very popular amplifiers had developed serious problems with stability and reliability. The major problem was the band switch which was purchased from Centralab or Oak and the very same switch used in other amplifiers was arcing when subjected to mild adverse conditions i.e. high line voltage and light loading. Production was halted and an emergency recall commenced. The configuration of one of the final band switch wafers was altered to provide a double gap rather than single. Several other critical changes were added and the production halt ceased. Much more to the story --- that to will be add here over time.

Note the first SR-2000 serial number, 452000 which is the prefix will become 452001 and finally 452002 to define the Engineering/run level. The part number on the lower right of the schematic will be 155-000348, 155-000348B, or 155-000348C distinguishing the EC/run level. Later in the manual we will define what to look for under the chassis to determine the level.

June, 22 1966 the first EC (C-331) was released to fix Bias, VFO, VOX, Feedback, 10 Meter receive problems, and a change that verified the closure of the antenna relay before transmit drivers were enabled.

June 29, 1966 EC (C-339) was released to fix 15 Meter tracking, S-Meter calibration, and additional final tank coil spacers to keep it from collapsing from heat.

November , 29 1996 an emergency stop shipment letter was released. The release will be issued on February , 6 1967 and will be explained in chronological order.

January, 4 1967 EC(C-380) was released to fix 6.5Mc feed thru, calibrator logic, and contact arcing on the 40M band.

January, 24 1967 the serial number was changed to 452001-X to reflect the changes that had been made. It was now a run 2 radio.

February, 6 1967 a release was issued stating that all shipped SR-2000’s must include all previous EC’s and a recall will be issued for all earlier SR-2000’s with serial number 452000-X for rework and upgrade to 452001-X. This was an emergency recall as severe damage was eminent caused by band switch arcing, bias failures, regeneration, and 6.5Mc feed through.

February ,22 1967 engineering change C-386 was issued.

When the loading capacitor was installed and the three mounting screws tightened, a warp occurred in the rotor and stator plates causing intermittent shorts. After tightening the mounting screws, the loading capacitor must be high potted at 600 VAC throughout rotation to verify no shorts occur. You will see how to determine the level of the radio, next, when we reach EC C-393.

March 17, 1967 engineering change C-393 was released. The intent was to reduce regeneration. Read all EC’s (A copy of the EC’s is available in the engineering changes section. A copper strap was added between the driver and RF shields and a pair of grounding springs were added to the bottom cover. Also the wire from the base of the final coil to the antenna relay is rerouted to the right of the coil (Facing the final cage from the front). It was parallel to the control wires routed through the final compartment, inducing enough RF to penetrate the feed through capacitors, allowing RF to reach the under chassis.

April 10, 1967 the serial numbers were changed to 452002 (Run three) to reflect engineering change C-393 was installed.

June 27, 1967 EC C-405 was released. Added a .01 uf capacitor across the plate current meter.

September 11, 1969 a service bulletin was released stating that R61 must be of a value that enables the blower to start at 110V.

August 23, 1971 service bulletin 1971-2 was released changing the final band switch.

 

C. Nuisance problems left unresolved --- None serious.

a. Regeneration.

b. Neutralizing problems.

c. Low transmit drive.

e. Noisy receive.

f. All and more will be addressed in the service notes section.

 

Chapter 2. THE CHARACTER OF THE SR-2000

A. Run 1/ Serial # 452000-xxxxx

Curt Hammond, Hallicrafters Vice president Marketing and Sales shipped the Run 1 SR-2000 to Albert Kahn, President of Electro-Voice for evaluation sometime before December of 1966. His response? “It is a fine piece of gear. Further, it is a bit difficult to tune when changing bands, needs a notch filter, WWV, and would like a CW filter”.

There is some evidence that a CW filter was added to a few trial radios and possibly a notch filter but I have not seen either in thirty years of searching.

Truth be told, the first SR-2000 had serious problems that appeared very soon after general availability. The best description is articulated in the EC’s that brought the radio to the run 2 level, serial # 452001- xxxx which corrected most of the identified problems..

B. Run 2/ Serial # 452001-xxxxx

The EC’s that were applied to bring the radio to run 2 can best be understood by reading the EC documentation and the above milestones.

C. Run 3/ Serial # 452002-xxxxx

This is the last and most current production level of the SR-2000 and when operating properly, is a very competitive radio in all categories. There were several non critical problems left when production ceased and the changes in the post production changes section of this manual correct or mitigate the problems that were left unresolved. I have regression tested each change and to the best of my knowledge all are sound.