hifienthusiast
Vintage by heart
I just finished replacing all the components of a pair of EL84 Rogers Junior monoblocks. They are quite different from the commonly found Leak TL12plus. The Junior uses a single ECC83 for phase splitting and driving a pair of EL84, while a TL12+ uses a separate EF86 as a driver and a ECC83 as a phase splitter.
I can only find one circuit diagram of a Japanses amp based on the Junior in the web:
http://www.tube-amps.net/EA_Hashimoto_EL84_PP_01.htm
Below is a photo of the underside before restoration:
I replaced every component since the old ones were out of spec, even the two filtering caps near the choke. The amps' value is not very high, so I don't care about using expensive components. All resistors are cheap carbon film types from RS or a store in Hong Kong and the caps are Solen, Rubycon and unknown brand.
Photo of the other Junior amp after restoration.
At beginning, there was a loud hum from one of them, I really didn't understand the problem until I measured all the nuts who earthed the connectors, the resistance between these "earthed" points were measured a few ohms to the chassis because of 50 year old rust. I just tightened every nut and the hum was a lot quieter to an acceptable level! There were obviously a few earth loops.
I am using a Meridian 507 CD player, EAR 834L pre and a pair of LS3/5a for all my vintage amps. The Juniors have the typical clarity of EL84 amps. They really shine on vocal reproduction, although the bass is not deep. The treble is bright and extended. I haven't used best components like PIO caps or expensive carbon film resistors like Dale, I am sure these designer parts will further improve the sound. However, I think I will stop replacing any component and just sit back and enjoy the amps!
Hon
I can only find one circuit diagram of a Japanses amp based on the Junior in the web:
http://www.tube-amps.net/EA_Hashimoto_EL84_PP_01.htm
Below is a photo of the underside before restoration:
I replaced every component since the old ones were out of spec, even the two filtering caps near the choke. The amps' value is not very high, so I don't care about using expensive components. All resistors are cheap carbon film types from RS or a store in Hong Kong and the caps are Solen, Rubycon and unknown brand.
Photo of the other Junior amp after restoration.
At beginning, there was a loud hum from one of them, I really didn't understand the problem until I measured all the nuts who earthed the connectors, the resistance between these "earthed" points were measured a few ohms to the chassis because of 50 year old rust. I just tightened every nut and the hum was a lot quieter to an acceptable level! There were obviously a few earth loops.
I am using a Meridian 507 CD player, EAR 834L pre and a pair of LS3/5a for all my vintage amps. The Juniors have the typical clarity of EL84 amps. They really shine on vocal reproduction, although the bass is not deep. The treble is bright and extended. I haven't used best components like PIO caps or expensive carbon film resistors like Dale, I am sure these designer parts will further improve the sound. However, I think I will stop replacing any component and just sit back and enjoy the amps!
Hon