Reel to reel  amplifier - Page 1
Forum section: electronics / general

author: pop982
author_rank: Newbie
timestamp: January 31, 2021, 04:52:20 pm
content: Hi i recently got hold of an old Akai x-360 reel to reel recorder with a built in amplifier but the left side has much less volume and almost no bass. I tried cleaning and measuring the volume, bass and treble pots but that didn't help. Anyone got any ideas what i could try?

author: GLouie
author_rank: Regular Contributor
timestamp: January 31, 2021, 05:15:15 pm
content: The service manual is available online, such as hifiengine.com.If you are looking for simple fixes, you should exercise each audio switch/button, especially any multi-pole switch for RECORD mode. In other words, operate each button several times, and put it into RECORD mode several times. I am unfamiliar with this model, but it is likely that it uses a multi-pole switch to change the circuitry from play to record mode, and these commonly get dirty and corrode over time.Check that the tape recording is good and the correct track format, and the heads clean and at least appear aligned correctly.Check the line outputs to determine if the problem is in the tape machine or the amplifier/speakers.

author: pop982
author_rank: Newbie
timestamp: January 31, 2021, 05:20:58 pm
content: Thanks for the anwser but the recorder works perfectly at line level and it is only when the internal amp is used that the problems start

author: ocw
author_rank: Regular Contributor
timestamp: January 31, 2021, 05:53:40 pm
content: It sounds like a bad DC blocking capacitor in the left audio path which has lost most of its capacitance--more likely an electrolytic...

author: james_s
author_rank: Super Contributor
timestamp: January 31, 2021, 06:53:41 pm
content: That was going to be my suggestion as well, coupling capacitor. A schematic will make your life much easier. A small test amplifier with AC coupled input is a handy troubleshooting tool for this sort of thing, you can buy a module for about $1 from China, or build something yourself with a LM386, or salvage something and then probe around and follow the signal to see where it degrades.

author: andy3055
author_rank: Super Contributor
timestamp: January 31, 2021, 07:25:44 pm
content: Given the age of those recorders, there are a few things you can try apart from what is suggested above.1. Make sure you clean and de-magnetize the PB head.2. Interchange the L/R output from the back of the PB head and see if it switches the fault. If it does, you may need a new head that may be almost impossible.If you have a scope, it will be very easy to pinpoint the defective area.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 31, 2021, 09:28:19 pm
content: Quote from: pop982 on January 31, 2021, 04:52:20 pmIf this is for tapes recorded on the same tape recorder, then it might be that the left channel is missing the AC bias during recording.Find a tape recorded properly and test if the defect is caused at playback, or at recording.

author: james_s
author_rank: Super Contributor
timestamp: January 31, 2021, 10:14:38 pm
content: He said it works perfectly using the line-out, making the last two suggestions moot. The problem is obviously somewhere between the line level and the output of the built in power amplifier.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 31, 2021, 10:21:38 pm
content: Should have wrote about the line out in the first post, I didn't read the whole thread, sorry.Indeed, it's not in the recording part, it's in the power amp then.