Hallicrafters SR-150, Operation And Maintenance Manual

By Walter Cates WD0GOF (UPDATE 10/30/2013)  

5  

1. SR-150 REFURBISHING AND REPAIRING  

  
SO YOU JUST GOT AN SR-150 FROM E-BAY OR SOMEONE THAT SAID “IT  
WORKED FINE THE LAST TIME I TURNED IT ON”. NOW WHERE DO YOU  
START? THE FOLLOWING PROCESS HAS EVOLVED OVER YEARS OF  
REFURBISHING THE SR-150. IT SHOULD BE FOLLOWED IN THE ORDER IT IS  
WRITTEN. THIS PROCEDURE IS DESIGNED TO PROGRESS IN AN ORDERLY  
MANNER TO MINIMIZE RUNNING IN CIRCLES. BE AWARE THIS IS NOT  
SOMETHING THAT IS ACCOMPLISHED WITH GREAT SPEED. THE AVERAGE 

TIME TO COMPLETION IS AROUND 60 HOURS. SOME HAVE TAKEN AS MUCH 
AS 200 HOURS, SOME AS FEW AS 20 HOURS.  

A complete cleaning and mechanical inspection is always advised. Cleaning of the rotary switches and the 

relays is of particular importance. Refer to the RIG CLEANING section for details. Look closely for broken or 
burned components. Check the rotation of the controls and mechanical stops of the main tuning dial. Try to 
eliminate the mechanical problem first. Inspect L32 for heat deformation on the close wound end. This is a high 
failure rate item when the rig is mistuned or misused in TX mode. See the PA LOADING COIL L32 section for 
repair details.  

1-1. RECAPPING;  

There are only four capacitors that are considered 

must replace

 components. They are C63, 5uf/25v, C100, 

5uf/25v, C114, 10uf/50v and C115, 2 X 30uf/350v. Capacitors C63, C114 and C115 each carry heavy current 
loads. Therefore the ESR rating of replacements is important. They should have an ESR rating of 1.0 ohms or 
less. ESR’s of 0.3 ohms and lower are available. This is not a place to save money. C115 is a dual cap. There 
are sources for this capacitor, 

but

 be careful. Some manufactures of these parts use inexpensive low quality 

parts. Don't buy from suppliers who will not quote or guarantee the ESR rating. Very low ESR individual 
capacitors are readily available. So replacing the dual cap with two capacitors under the chassis is sometimes a 
better solution. Generally speaking shotgun replacement of the paper caps is not recommended.  

1-2. RELAYS  

Relays K2 and K3 are the most problematic components in the 150. Relay K1, not so much, usually all it needs 

is contact cleaning. Relays K2 and K3 in parallel provide approximately 380 ohms resistance for the cathode of 
V13. So the common 12vdc relay will 

not

 substitute for them. Years of misuse and spraying with contact 

cleaner has warped the contact substrate of K2 and K3. 

Rule #1 for relays

 is never spray relays with anything. 

Rule #2

 never use sandpaper on the contacts. You can test them in the rig using a VOM, two clip leads and a 10 

volt supply. More often than not they need to be removed repaired and reinstalled. Go to RELAY TEST AND 
REPAIR section for information on how this is accomplished. They need to be verified as operational before 
you proceed to the next step in this process.  

1-3. AFTER MARKET MODIFICATIONS  

If you find any modifications, re-wirings or added components remove them and return the rig to the original 

configuration.