Akai 1731W Reel 2 Reel Channel Rec Issue - Page 1
Forum section: electronics / repair

author: wblackledg
author_rank: Regular Contributor
timestamp: September 25, 2017, 02:32:44 am
content: I picked up an Akai 1731W at an estate sale today.Almost everything works.However, the left channel is the only one that you can record on.Audio passes thru the right side, but it doesn't record. Overwriting previously recorded Audio works but When you do record, the right channel is just blank.So its like the signal is making it out of the recorder and the unit is attempted to record, but no signal is making it to the tape head?ideas?thanks.

author: wblackledg
author_rank: Regular Contributor
timestamp: September 25, 2017, 07:00:29 pm
content: Can someone recommend a repair forum site for old vintage stuff like this?thanks.

author: Gyro
author_rank: Super Contributor
timestamp: September 25, 2017, 07:25:35 pm
content: Tryhttp://www.vintage-radio.net/forum/index.phpSpecifically the 'Vintage Tape' forum (obviously) but most of them are worth a read.

author: Armadillo
author_rank: Super Contributor
timestamp: September 25, 2017, 07:26:14 pm
content: hi;Firstly you see the mode switch pc board, you will need to clean clean and clean all the switches contacts with contact cleaner and eraser.Then;If you have an oscilloscope, you can probe Pin 15 just to make sure that signal is trying to go the right side head. The signal should be the same as Pin 16 to left side head.Then you probe at J19 Pin 4 to make sure that signal arrives at the right side head safely.Then;99% sure it will record. In case not, the head is defective, change the head.If you don't have a scope, you can use a audible signal tracer.Hopes it help.

author: wblackledg
author_rank: Regular Contributor
timestamp: September 27, 2017, 01:54:28 am
content: Quote from: Gyro on September 25, 2017, 07:25:35 pmthanks so much for responding.

author: wblackledg
author_rank: Regular Contributor
timestamp: September 27, 2017, 01:58:47 am
content: Quote from: Armadillo on September 25, 2017, 07:26:14 pmthank you very very much. Yes, I have a scope. Its a funny story, when Dave was doing his "old scope follow up video" , he showed my exact Textronix scope on ebay as he was scrolling. I got for $100.Now I have to dig it out of the garage. My wife decided my work bench needed to be a "flower stand". Luckily she killed all the plants and flowers so its time to reclaim it..thanks again.

author: Old Don
author_rank: Regular Contributor
timestamp: September 27, 2017, 11:58:30 am
content: Or if you can quickly swap output cables to the two head channels and the dead channel is still dead then the head needs changing. Just a couple of minutes of soldering can give you a go-no go on what to replace or clean.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: September 27, 2017, 12:09:42 pm
content: AlsoTapeHeads forumis a good place on all tape related things.CheersAlex

author: wblackledg
author_rank: Regular Contributor
timestamp: September 27, 2017, 01:54:40 pm
content: Quote from: Old Don on September 27, 2017, 11:58:30 amThese things are the easiest to find parts for. lots of stuff on ebay, but I haven't seen another source except craigslist, meaning you by two and one is for parts.

author: wblackledg
author_rank: Regular Contributor
timestamp: September 27, 2017, 02:04:52 pm
content: Quote from: Alex Nikitin on September 27, 2017, 12:09:42 pmthanks for the link. I'm checking them out now.

author: BMack
author_rank: Regular Contributor
timestamp: September 29, 2017, 05:12:46 am
content: If you touch the pins on the record head in question with a screwdriver you will hear a hum, do that on the side in question. If that hum records, it's not the record head...down and dirty way to do it, learned that from an old tech with 50 years in the business.Before you do too much, take off the face plate and look at the switch assembly. That is a cast piece of metal and that part breaks a LOT. If there are any hairline cracks start looking for the part because that will fail at some point. Pics attached of the most recent.

author: wblackledg
author_rank: Regular Contributor
timestamp: September 29, 2017, 01:38:01 pm
content: Quote from: BMack on September 29, 2017, 05:12:46 amthanks for responding.when you say the pins, you mean on on the circuit board or on on the outside of the head itself?thanks.

author: BMack
author_rank: Regular Contributor
timestamp: September 30, 2017, 08:11:05 pm
content: Quote from: wblackledg on September 29, 2017, 01:38:01 pmWhere the four wires connect to the head, where they are soldered.

author: wblackledg
author_rank: Regular Contributor
timestamp: September 30, 2017, 08:15:14 pm
content: Great! thanks!

author: BMack
author_rank: Regular Contributor
timestamp: October 03, 2017, 04:49:25 am
content: Quote from: wblackledg on September 30, 2017, 08:15:14 pmIf you need a record head, I may have one. I had to part one of my personal units out because of a bad motor and it had some bad vacuum tubes...I'm not sure if the heads cross to yours but it's worth a look. I'd be super reasonable in price, I'm still backwards on the unit or I'd give it to you.

author: floobydust
author_rank: Super Contributor
timestamp: October 03, 2017, 07:19:30 am
content: bmack, touching the record head pins does not have enough signal (hum) to write to mag tape. So I'm not following what you are doing, unless it's a playback problem.98/100 times it's oxide on the record/play switch. These are multi-pole switches that redirect many signals including the record amplifier and bias oscillator. You can try move the switch internally a dozen times and see if it cleans it off, or use contact cleaner.

author: wblackledg
author_rank: Regular Contributor
timestamp: October 03, 2017, 11:49:47 am
content: Quote from: BMack on October 03, 2017, 04:49:25 amthanks, I will let you know. Honey-dos got in the way of a repair plan..

author: wblackledg
author_rank: Regular Contributor
timestamp: October 03, 2017, 11:51:05 am
content: Quote from: floobydust on October 03, 2017, 07:19:30 amwhen trying to record, it does record, but only blank sound on the one track/channel. No noise. I don't know if thats a good thing or it means nothing.

author: BMack
author_rank: Regular Contributor
timestamp: October 03, 2017, 06:03:46 pm
content: Quote from: wblackledg on October 03, 2017, 11:51:05 amThat means the erase head is working.

author: wblackledg
author_rank: Regular Contributor
timestamp: October 03, 2017, 06:19:14 pm
content: Quote from: BMack on October 03, 2017, 06:03:46 pm

author: BMack
author_rank: Regular Contributor
timestamp: October 03, 2017, 06:20:02 pm
content: Quote from: floobydust on October 03, 2017, 07:19:30 amYou know, you might be right, I'd have to recheck. It's been several years since I had one with a record problem, mostly it's general maintenance, motor problems(or speed control) or playback. I could have sworn that I did that and heard a difference but I could be wrong.You could check with a scope or signal/audio tracer to see if the signal is getting to the record head. I actually like the signal tracer to do stuff like this because you can hear what is getting there and you don't need to connect the signal generator. The shop has an old Heathkit signal tracer but I made one for myself with a cheap bluetooth speaker.

author: floobydust
author_rank: Super Contributor
timestamp: October 03, 2017, 08:59:26 pm
content: I'm just reluctant to say "the head is defective".OP could measure head continuity after the REC/PLAY switch at the second pcb (have to demagnetize afterwards).There's a connector at the head block, REC/PLAY switch and shielded cable wires that could have failed.I've seen shielded cable wires break off right at the heads.Sometimes aggressive tape head demagnetizers generate enough voltage to damage the semi's.

author: BMack
author_rank: Regular Contributor
timestamp: October 04, 2017, 01:56:09 am
content: Quote from: floobydust on October 03, 2017, 08:59:26 pmI agree, that's why I originally tried to get him to rule it out quickly.

author: Old Don
author_rank: Regular Contributor
timestamp: October 07, 2017, 01:28:52 am
content: I earlier suggested wiring the dead side head to the working side's electronics. You can quickly determine if the electronics is dead or the head is dead this way. If the problem continues then the head is dead. If not then the electronics for the dead side is the problem. You don't even need to wire the other side up since you know that head and electronics was working together and so it has to be either the head or the electronics for the dead side that is OOC. Simple and quick way to eliminate one or the other so you can proceed with the necessary repairs. I guess you could maybe jump the two heads as a quick test if that won't overload the electronics and see if both channels have some (reduced level) recording too.

author: wblackledg
author_rank: Regular Contributor
timestamp: October 07, 2017, 02:32:17 am
content: Quote from: Old Don on October 07, 2017, 01:28:52 amthanks, some honey-dos got in the way, hopefully this week...

author: Old Don
author_rank: Regular Contributor
timestamp: October 11, 2017, 03:02:05 pm
content: Completely understand honey-do's, I've got a SWMBO too. Plus while I'm "retired", I also belong to a half dozen organizations that take up most of rest of my awake hours.