Tuner Alignment

[Daiana Parthemore]

TheHitachi service manual, which incidentally is excellent, sets up the discriminator initially as step 2 of 9 using the usual sweep generator / scope / wobulator. The distortion test is a fine tune at step 6.

Frequency response; the generator may not have the appropriate pre-emphasis and this become a double edged sword since if it does a flat signal will overmodulate above 2 KHz. US tuners are 75 uS and EU (and other parts of the world ) are 50 uS. Most of the little car FM modulators are also 50 uS. And then the 19 KHz pilot filter is a hard bandstop at the top of the band. Maybe Matt can create a test sweep with the 75 uS pre-emphasis incorporated to get a flat response from the tuner? And stop the sweep before it triggers the pilot detector.

This is great info. My SG80 signal generator is new to me, and I have been missing some cables. Just got them in the mail yesterday, so plan on hooking things up to see what kind of test results I get. As you said, the actual goal in alignment when using the Distortion Analyzer is to simply adjust to minimum distortion. So absolute values are not that important. Your setup parameters will be helpful in getting to an initial setup. Thanks, again!

Yes and no on the reemphasis. FM has a specific limit on modulation so if you sweep with preemphasis on you will overmodulate or run at a reduced level. You can add back boost on the output, but probably best done with a correction curve, something that the QA401 supports. I would need Matt to show how in this application. Also the distortion is sensitive to the IF bandwidth. Meaning that low distortion wide bandwidth need strong local stations.

Following on from earlier posts,I eventually got around to building a FM Stereo Test Unit based on a Pira CZ Stereo Encoder bought through eBay and an active switchable pre-emphasis filter. This is it in a not quite completed state:

FM Stereo - 1640640 167 KB

Older Marantz tuners are legendary for their warm, smooth sounds and their ability to separate stations packed closely together, This selectivity is something much-needed in North America during the peak in FM radio the 70s.

Marantz spared little expense when they designed this tuner and it shows when you lift the lid. Each circuit block is packed into its own shielded metal sub-block and all adjustments are clearly marked.

The work on my Marantz 125 centred around two areas: precision alignment and replacement of critical parts in the circuit. Looking at the parts first, I paid extra attention to the power supply and signal path.

In the power supply, I removed all the original electrolytic capacitors and replaced them with premium, low-ESR, high-spec parts. In the signal path, specifically in the output buffer, I replaced all the electrolytic coupling capacitors with much better-sounding film capacitors.

The second and critical part of the process is the precision alignment of the FM front-end IF stages and stereo demodulator. This alignment process is what often brings the biggest performance gains to FM tuners because they are complex electro-mechanical systems and they drift over time.

Often they are not even that carefully aligned from the factory and sometimes huge gains can be realised by a careful alignment, utilizing my precision laboratory equipment, specifically designed to aid in this sort of work.

Hi Randall, thanks for your positive feedback, much appreciated. The Jelco arm works very well on the Kenwood, but you will need to make up an arm mounting board to suit. In terms of supplying the tonearm, you would be best to have a look on eBay, set to an international search. You will be able to get one cheaper this way, by dealing directly with a supplier. Kind regards, Mike.

I have a Marantz 2270 that i am about to restore. I would like to align the fm and am sections once the job is done but don't own the equipment to do it nor have i ever aligned a tuner before. I very rarely listen to radio so if i can't find anyone to do the job i will just leave it be. But if anyone knows of someone capable of doing this job in Tasmania that would be great. I'm not keen on shipping this one interstate, the risk of damage in transit is not worth it to me when it comes to radio performance.

I have the service manual but unfortunately i don't have an Am signal generator, fm signal generator and a stereo modulator to do that job and i have no experience with aligning radios so even with the tools i'd probably just make a mess of it. The actual rebuild of the amplifier is no problem for me but radios are a form of black magic to me.

As far as i am aware you can try such methods and make them work but to get optimal performance you need to make all the adjustments in the service manual with a scope and the required signal generators etc. Replacing electrolytic caps in the circuit can also throw the alignment off a little. I'll more then likely just leave it as it is as i never listen to the radio, its more of a case of when i do a job i like to make everything function optimally.

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ARCHIVED TOPIC: Banjo 5th string tuner loose and alignment question

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I have a GoldTone BG 250 I purchased at the Titusville, Florida factory around 20 years ago. A couple of months ago I was tuning the banjo and the 5th string nut broke. (photo). I had it replaced with a bone nut.

Today I had need to remove and replace the 5th string and I noticed the tuner was loose in the neck and came off easily. Pressing and lightly tapping it back in was no help as the tuner remains loose in the bore. (photo)

With the tuner pushed in-place there is an offset between the 5th string alignment and the tuner hub.(photo) My guess is that this misalignment caused a sideways force on the nut resulting in breakage.

Is the tuner hub and string supposed to be in closer alignment? Any suggestions on re-installing the tuner to fit snugly? Thanks all.

Back in the 1960's I was standing in a small group of guys talking to Don Reno while he changed the strings on "Old Nellie". When he took the 5th string off, the tuner fell right out onto the ground. He just picked it up, shoved it back in the hole and put the string on. After that, I never worried about the 5th string tuner. You can fit it perfectly, glue it in or "stick it in the hole" like Don did. All of them work. Once there is tension on the string, the tuner will stay in place, unless the hole is so large it turns around in it.

Your original fifth string nut lasted twenty years and it appears that it was installed with the string slot cut a bit to the outside which is most likely why it broke. I'd say twenty years with a poorly slotted original fifth string nut isn't all that bad a deal.

What you have to ascertain now is WHY the tuner which has been snug in its bore for twenty years is now loose. It sounds like it isn't seating in the bore properly, so I'd look very carefully in the bore for a small glue lip or other anomaly that is preventing the splined housing shaft from locking in place. Once it goes that tiny bit further in then that will most likely take care of the slight misalignment between the fifth string tuner capstan and the fifth string nut slot.

If your fifth string tuner has one of the splines larger than the others make sure it's aligned with the hole properly so the tuner will seat as it is supposed to. The "fin" spline can prevent the tuner from seating if it isn't oriented properly.

That tuner looks to be sitting too high. I don't think the hole was reamed sufficiently deep enough. It may also be the cause of the nut breaking over time. Given that the string was pulling upwards in the pip (nut).

Remember the BG250 is a competitive spec. banjo, so things like alignment can be an issue.

Once upon a time, I was changing strings and the nut fell off, the 5th string tuner come out, the tailpiece came off and what the heck?

You remove the tuner button and washer. I use a 1/4" drive 5/16" deep socket to set down over the tuner post so you can tap the body of the tuner in. Use some white Glue. Try to bring the flutes on the tuner socket as close to the neck as possible..

If your tuner has a key spline: GRIND IT OFF.

The tuning gang will have sets of small blades and sets of larger blades- the AM sections are the larger blades. In the event you have a set of blades that have about the same number of blades as the larger blades, but is a little bit smaller- this smaller set is the oscillator section. adjusting that will move where the AM stations line up on the dial.

On some recievers, usually the expensive units, they are in a plastic case with mylar between the blades. These will have 2 or 4 trimmers on the back side of these. Typically AM or FM is going to be diagonal from each other. In these units, one is always the oscillator and you will spot it because the stations will change. Otherwise these are adjusted as above for peak signal.

In the end what your goal is: 1) To tweek the trimmers to achieve maximum sensitivity by matching the reciever to the antenna you have in use. As the first step and as you make other adjustments, you want to peak the signal. 2) Have linearity of tuning across the dial face. 3) Have the stations line up where they are supposed to on the dial.

The first few times may be agravating. There are times when only slight tweeks need to be made, and once you get used to making the adjustments, if you do it correctly, you can tune up the AM section very quickly.

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